General Description
The MAX1340/MAX1342/MAX1346/MAX1348 integrate a
multichannel, 12-bit, analog-to-digital converter (ADC)
and a quad, 12-bit, digital-to-analog converter (DAC) in a
single IC. The devices also include a temperature sensor
and configurable general-purpose I/O ports (GPIOs) with
a 25MHz SPI™-/QSPI™-/MICROWIRE™-compatible seri-
al interface. The ADC is available in a 4 or an 8 input-
channel version. The four DAC outputs settle within 2.0µs,
and the ADC has a 225ksps conversion rate.
All devices include an internal reference (4.096V) provid-
ing a well-regulated, low-noise reference for both the
ADC and DAC. Programmable reference modes for the
ADC and DAC allow the use of an internal reference, an
external reference, or a combination of both. Features
such as an internal ±1°C accurate temperature sensor,
FIFO, scan modes, programmable internal or external
clock modes, data averaging, and AutoShutdown™ allow
users to minimize both power consumption and proces-
sor requirements. The low glitch energy (4nV•s) and low
digital feedthrough (0.5nV•s) of the integrated quad
DACs make these devices ideal for digital control of fast-
response closed-loop systems.
The devices are guaranteed to operate with a supply
voltage from +4.75V to +5.25V The devices consume
2.5mA at 225ksps throughput, only 22µA at 1ksps
throughput, and under 0.2µA in the shutdown mode. The
MAX1342/MAX1348 offer four GPIOs that can be config-
ured as inputs or outputs.
The MAX1340/MAX1342/MAX1346/MAX1348 are avail-
able in 36-pin thin QFN packages. All devices are speci-
fied over the -40°C to +85°C temperature range.
Applications
Closed-Loop Controls for Optical Components
and Base Stations
System Supervision and Control
Data-Acquisition Systems
Features
♦12-Bit, 225ksps ADC
Analog Multiplexer with True-Differential
Track/Hold (T/H)
8 Single-Ended Channels or 4 Differential
Channels (Unipolar or Bipolar)
(MAX1340/MAX1342)
4 Single-Ended Channels or 2 Differential
Channels (Unipolar or Bipolar)
(MAX1346/MAX1348)
Excellent Accuracy: ±0.5 LSB INL, ±0.5 LSB DNL
♦12-Bit, Quad, 2µs Settling DAC
Ultra-Low Glitch Energy (4nV•s)
Power-Up Options from Zero Scale or Full Scale
Excellent Accuracy: ±0.5 LSB INL
♦Internal Reference or External Single-Ended/
Differential Reference
Internal Reference Voltage (4.096V)
♦Internal ±1°C Accurate Temperature Sensor
♦On-Chip FIFO Capable of Storing 16 ADC
Conversion Results and One Temperature Result
♦On-Chip Channel-Scan Mode and Internal
Data-Averaging Features
♦Analog Single-Supply Operation
+4.75V to +5.25V
♦Digital Supply: 2.7V to AVDD
♦25MHz, SPI/QSPI/MICROWIRE Serial Interface
♦AutoShutdown Between Conversions
♦Low-Power ADC
2.5mA at 225ksps
22µA at 1ksps
0.2µA at Shutdown
♦Low-Power DAC: 1.5mA
♦Evaluation Kit Available (Order MAX1258EVKIT)
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
________________________________________________________________
Maxim Integrated Products
1
Ordering Information/Selector Guide
19-3332; Rev 3; 3/08
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
Pin Configurations appear at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
REF
VOLTAGE
(V)
ANALOG
SUPPLY
VOLTAGE (V)
RESOLUTION
BITS**
ADC
CHANNELS
DAC
CHANNELS GPIOs
MAX1340BETX -40°C to +85°C 36 Thin QFN-EP* 4.096 4.75 to 5.25 12 8 4 0
MAX1342BETX -40°C to +85°C 36 Thin QFN-EP* 4.096 4.75 to 5.25 12 8 4 4
MAX1346BETX -40°C to +85°C 36 Thin QFN-EP* 4.096 4.75 to 5.25 12 4 4 0
MAX1348BETX -40°C to +85°C 36 Thin QFN-EP* 4.096 4.75 to 5.25 12 4 4 4
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
*
EP = Exposed pad.
**
Number of resolution bits refers to both DAC and ADC.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
AVDD to AGND .........................................................-0.3V to +6V
DGND to AGND.....................................................-0.3V to +0.3V
DVDD to AVDD .......................................................-3.0V to +0.3V
Digital Inputs to DGND.............................................-0.3V to +6V
Digital Outputs to DGND .........................-0.3V to (DVDD + 0.3V)
Analog Inputs, Analog Outputs and REF_
to AGND...............................................-0.3V to (AVDD + 0.3V)
Maximum Current into Any Pin (except AGND, DGND, AVDD,
DVDD, and OUT_) ...........................................................50mA
Maximum Current into OUT_.............................................100mA
Continuous Power Dissipation (TA= +70°C)
36-Pin Thin QFN (6mm x 6mm)
(derate 26.3mW/°C above +70°C)......................2105.3mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-60°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
ADC
DC ACCURACY (Note 1)
Resolution 12 Bits
Integral Nonlinearity INL ±0.5 ±1.0 LSB
Differential Nonlinearity DNL ±0.5 ±1.0 LSB
Offset Error ±0.5 ±4.0 LSB
Gain Error (Note 2) ±0.5 ±4.0 LSB
Gain Temperature Coefficient ±0.8 ppm/°C
Channel-to-Channel Offset ±0.1 LSB
DYNAMIC SPECIFICATIONS (10kHz sine-wave input, VIN = 4.096VP-P, 225ksps, fCLK = 3.6MHz)
Signal-to-Noise Plus Distortion SINAD 70 dB
Total Harmonic Distortion
(Up to the Fifth Harmonic) THD -76 dBc
Spurious-Free Dynamic Range SFDR 72 dBc
Intermodulation Distortion IMD fIN1 = 9.9kHz, fIN2 = 10.2kHz 76 dBc
Full-Linear Bandwidth SINAD > 70dB 100 kHz
Full-Power Bandwidth -3dB point 1 MHz
CONVERSION RATE (Note 3)
External reference 0.8 µs
Power-Up Time tPU Internal reference (Note 4) 218
C onver si on
C l ock
C ycl es
Note: If the package power dissipation is not exceeded, one output at a time may be shorted to AVDD, DVDD, AGND, or DGND
indefinitely.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Acquisition Time tACQ (Note 5) 0.6 µs
Internally clocked 5.5
Conversion Time tCONV Externally clocked 3.6 µs
External-Clock Frequency fCLK Externally clocked conversion (Note 5) 0.1 3.6 MHz
Duty Cycle 40 60 %
Aperture Delay 30 ns
Aperture Jitter < 50 ps
ANALOG INPUTS
Unipolar 0 VREF
Input-Voltage Range (Note 6) Bipolar -VREF/2 VREF/2 V
Input Leakage Current ±0.01 ±1 µA
Input Capacitance 24 pF
INTERNAL TEMPERATURE SENSOR
TA = +25°C ±0.7
Measurement Error (Notes 5, 7) TA = TMIN to TMAX ±1.0 ±3.0 °C
Temperature Resolution 1/8 °C/LSB
INTERNAL REFERENCE
REF1 Output Voltage (Note 8) 4.066 4.096 4.126 V
REF1 Voltage Temperature
Coefficient TCREF ±30 ppm/°C
REF1 Output Impedance 6.5 kΩ
REF1 Short-Circuit Current VREF = 4.096V 0.63 mA
EXTERNAL REFERENCE
REF1 Input-Voltage Range VREF1 REF mode 11 (Note 4) 1 AVDD +
0.05 V
REF mode 01 1 AVDD +
0.05
REF2 Input-Voltage Range
(Note 4) VREF2
REF mode 11 0 1
V
VREF = 4.096V, fSAMPLE = 225ksps 40 80
REF1 Input Current (Note 9) IREF1 Acquisition between conversions ±0.01 ±1 µA
VREF = 4.096V, fSAMPLE = 225ksps 40 80
REF2 Input Current IREF2 Acquisition between conversions ±0.01 ±1 µA
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
4 _______________________________________________________________________________________
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DAC
DC ACCURACY (Note 10)
Resolution 12 Bits
Integral Nonlinearity INL ±0.5 ±4 LSB
Differential Nonlinearity DNL Guaranteed monotonic ±1.0 LSB
Offset Error VOS (Note 8) ±3 ±10 mV
Offset-Error Drift ±10 ppm of
FS/°C
Gain Error GE (Note 8) ±5 ±10 LSB
Gain Temperature Coefficient ±8 ppm of
FS/°C
DAC OUTPUT
No load 0.02 AVDD -
0.02
Output-Voltage Range
10kΩ load to either rail 0.1 AVDD -
0.1
V
DC Output Impedance 0.5 Ω
Capacitive Load (Note 11) 1 nF
Resistive Load to AGND RLAVDD = 4.75V, VREF = 4.096V, gain error
< 2% 500 Ω
From power-down mode, AVDD = 5V 25
Wake-Up Time (Note 12) From power-down mode, AVDD = 2.7V 21 µs
1kΩ Output Termination Programmed in power-down mode 1 kΩ
100kΩ Output Termination At wake-up or programmed in
power-down mode 100 kΩ
DYNAMIC PERFORMANCE (Notes 5, 13)
Output-Voltage Slew Rate SR Positive and negative 3 V/µs
Output-Voltage Settling Time tSTo 1 LSB, 400 - C00 hex (Note 7) 2 5 µs
Digital Feedthrough Code 0, all digital inputs from 0 to DVDD 0.5 nV•s
Major Code Transition Glitch
Impulse Between codes 2047 and 2048 4 nV•s
From VREF 660
Output Noise (0.1Hz to 50MHz) Using internal reference 720 µVP-P
From VREF 260
Output Noise (0.1Hz to 500kHz) Using internal reference 320 µVP-P
DAC-to-DAC Transition
Crosstalk 0.5 nV•s
ELECTRICAL CHARACTERISTICS (continued)
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
_______________________________________________________________________________________ 5
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INTERNAL REFERENCE
REF1 Output Voltage 4.066 4.096 4.126 V
REF1 Temperature Coefficient TCREF ±30 ppm/°C
REF1 Short-Circuit Current VREF = 4.096V 0.63 mA
EXTERNAL-REFERENCE INPUT
REF1 Input-Voltage Range VREF1 REF modes 01, 10, and 11 (Note 4) 0.7 AVDD V
REF1 Input Impedance RREF1 70 100 130 kΩ
DIGITAL INTERFACE
DIGITAL INPUTS (SCLK, DIN, CS, CNVST, LDAC)
Input-Voltage High VIH DVDD = 2.7V to 5.25V 2.4 V
DVDD = 3.6V to 5.25V 0.8
Input-Voltage Low VIL DVDD = 2.7V to 3.6V 0.6 V
Input Leakage Current IL±0.01 ±10 µA
Input Capacitance CIN 15 pF
DIGITAL OUTPUT (DOUT) (Note 14)
Output-Voltage Low VOL ISINK = 2mA 0.4 V
Output-Voltage High VOH ISOURCE = 2mA DVDD -
0.5 V
Tri-State Leakage Current ±10 µA
Tri-State Output Capacitance COUT 15 pF
DIGITAL OUTPUT (EOC) (Note 14)
Output-Voltage Low VOL ISINK = 2mA 0.4 V
Output-Voltage High VOH ISOURCE = 2mA DVDD -
0.5 V
Tri-State Leakage Current ±10 µA
Tri-State Output Capacitance COUT 15 pF
DIGITAL OUTPUTS (GPIO_) (Note 14)
ISINK = 2mA 0.4
GPIOC_ Output-Voltage Low ISINK = 4mA 0.8 V
GPIOC_ Output-Voltage High ISOURCE = 2mA DVDD -
0.5 V
GPIOA_ Output-Voltage Low ISINK = 15mA 0.8 V
GPIOA_ Output-Voltage High ISOURCE = 15mA DVDD -
0.8 V
Tri-State Leakage Current ±10 µA
Tri-State Output Capacitance COUT 15 pF
ELECTRICAL CHARACTERISTICS (continued)
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
6 _______________________________________________________________________________________
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER REQUIREMENTS (Note 15)
Digital Positive-Supply Voltage DVDD 4.75 AVDD V
Idle, all blocks shut down 0.2 4 µA
Digital Positive-Supply Current DIDD Only ADC on, external reference 1 mA
Analog Positive-Supply Voltage AVDD 4.75 5.25 V
Idle, all blocks shut down 0.2 2 µA
fSAMPLE = 225ksps 2.8 4.2
Only ADC on,
external reference fSAMPLE = 100ksps 2.6
Analog Positive-Supply Current AIDD
All DACs on, no load, internal reference 1.5 4.0
mA
REF1 Positive-Supply Rejection PSRR AVDD = 4.75V -80 dB
DAC Positive-Supply Rejection PSRD Output code = FFFhex, AVDD = 4.75V to
5.25V ±0.1 ±0.5 mV
ADC Positive-Supply Rejection PSRA Full-scale input, AVDD = 4.75V to 5.25V ±0.06 ±0.5 mV
TIMING CHARACTERISTICS (Figures 6–13)
SCLK Clock Period tCP 40 ns
SCLK Pulse-Width High tCH 40/60 duty cycle 16 ns
SCLK Pulse-Width Low tCL 60/40 duty cycle 16 ns
GPIO Output Rise/Fall After
CS Rise tGOD CLOAD = 20pF 100 ns
GPIO Input Setup Before CS Fall tGSU 0ns
LDAC Pulse Width tLDACPWL 20 ns
CLOAD = 20pF, SLOW = 0 1.8 12.0
SCLK Fall to DOUT Transition
(Note 16) tDOT CLOAD = 20pF, SLOW = 1 10 40 ns
CLOAD = 20pF, SLOW = 0 1.8 12.0
SCLK Rise to DOUT Transition
(Notes 16, 17) tDOT CLOAD = 20pF, SLOW = 1 10 40 ns
CS Fall to SCLK Fall Setup Time tCSS 10 ns
S C LK Fal l to CS Ri se S etup Ti m et
CSH 0 2000 ns
DIN to SCLK Fall Setup Time tDS 10 ns
DIN to SCLK Fall Hold Time tDH 0ns
CS Pulse-Width High tCSPWH 50 ns
CS Rise to DOUT Disable tDOD CLOAD = 20pF 25 ns
CS Fall to DOUT Enable tDOE CLOAD = 20pF 1.5 25.0 ns
EOC Fall to CS Fall tRDS 30 ns
ELECTRICAL CHARACTERISTICS (continued)
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
_______________________________________________________________________________________ 7
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CKSEL = 01 (temp sense) or CKSEL =
10 (temp sense), internal reference on 65
CKSEL = 01 (temp sense) or CKSEL =
10 (temp sense), internal reference
initially off
140
CKSEL = 01 (voltage conversion) 9
CKSEL = 10 (voltage conversion),
internal reference on 9
CS or CNVST Rise to EOC Fall—
Internally Clocked
Conversion Time
tDOV
CKSEL = 10 (voltage conversion),
internal reference initially off 80
µs
CKSEL = 00, CKSEL = 01 (temp sense) 40 ns
CNVST Pulse Width tCSW CKSEL = 01 (voltage conversion) 1.4 µs
ELECTRICAL CHARACTERISTICS (continued)
(AVDD = DVDD = 4.75V to 5.25V, external reference VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), TA = -40°C to +85°C, unless
otherwise noted. Typical values are at AVDD = DVDD = 5V, TA= +25°C. Outputs are unloaded, unless otherwise noted.)
Note 1: Tested at DVDD = AVDD = +5.25V.
Note 2: Offset nulled.
Note 3: No bus activity during conversion. Conversion time is defined as the number of conversion clock cycles, multiplied by the
clock period.
Note 4: See Table 5 for reference-mode details.
Note 5: Not production tested. Guaranteed by design.
Note 6: See the
ADC/DAC References
section.
Note 7: Fast automated test, excludes self-heating effects.
Note 8: Specified over the -40°C to +85°C temperature range.
Note 9: REFSEL[1:0] = 00 or when DACs are not powered up.
Note 10: DAC linearity, gain, and offset measurements are made between codes 115 and 3981.
Note 11: The DAC buffers are guaranteed by design to be stable with a 1nF load.
Note 12: Time required by the DAC output to power up and settle within 1 LSB in the external reference mode.
Note 13: All DAC dynamic specifications are valid for a load of 100pF and 10kΩ.
Note 14: Only one digital output (either DOUT, EOC, or the GPIOs) can be indefinitely shorted to either supply at one time.
Note 15: All digital inputs at either DVDD or DGND. DVDD should not exceed AVDD.
Note 16: See the
Reset Register
section and Table 9 for details on programming the SLOW bit.
Note 17: Clock mode 11 only.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
8 _______________________________________________________________________________________
Typical Operating Characteristics
(AVDD = DVDD = 5V, external VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), fSAMPLE = 225ksps, CLOAD = 50pF, 0.1µF capacitor
at REF, TA= +25°C, unless otherwise noted.)
0
0.1
0.3
0.2
0.4
0.5
ANALOG SHUTDOWN CURRENT
vs. ANALOG SUPPLY VOLTAGE
MAX1340 toc01
SUPPLY VOLTAGE (V)
ANALOG SHUTDOWN CURRENT (µA)
4.750 5.0004.875 5.125 5.250
0.4
0.3
0.2
0.1
0
-40 10-15 35 60 85
ANALOG SHUTDOWN CURRENT
vs. TEMPERATURE
MAX1340 toc02
TEMPERATURE (°C)
ANALOG SHUTDOWN CURRENT (µA)
ADC INTEGRAL NONLINEARITY
vs. OUTPUT CODE
MAX1340 toc03
OUTPUT CODE
INTEGRAL NONLINEARITY (LSB)
307220481024
-0.75
-0.50
-0.25
0
0.25
0.50
0.75
1.00
-1.00
0 4096
ADC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
MAX1340 toc04
OUTPUT CODE
DIFFERENTIAL NONLINEARITY (LSB)
307220481024
-0.75
-0.50
-0.25
0
0.25
0.50
0.75
1.00
-1.00
04096
0
0.2
0.6
0.4
0.8
1.0
ADC OFFSET ERROR
vs. ANALOG SUPPLY VOLTAGE
MAX1340 toc05
SUPPLY VOLTAGE (V)
OFFSET ERROR (LSB)
4.750 5.0004.875 5.125 5.250
2
1
0
-1
-2
-40 10-15 35 60 85
ADC OFFSET ERROR
vs. TEMPERATURE
MAX1340 toc06
TEMPERATURE (°C)
OFFSET ERROR (LSB)
1.0
0.5
0
-0.5
-1.0
4.750 5.0004.875 5.125 5.250
ADC GAIN ERROR
vs. ANALOG SUPPLY VOLTAGE
MAX1340 toc07
SUPPLY VOLTAGE (V)
GAIN ERROR (LSB)
2
1
0
-1
-2
-40 10-15 35 60 85
ADC GAIN ERROR
vs. TEMPERATURE
MAX1340 toc08
TEMPERATURE (°C)
GAIN ERROR (LSB)
ADC EXTERNAL REFERENCE
INPUT CURRENT vs. SAMPLING RATE
MAX1340 toc09
SAMPLING RATE (ksps)
ADC EXTERNAL REFERENCE INPUT CURRENT (µA)
25020015010050
10
20
30
40
50
60
0
0300
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
_______________________________________________________________________________________ 9
Typical Operating Characteristics (continued)
(AVDD = DVDD = 5V, external VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), fSAMPLE = 225ksps, CLOAD = 50pF, 0.1µF capacitor
at REF, TA= +25°C, unless otherwise noted.)
ANALOG SUPPLY CURRENT
vs. SAMPLING RATE
MAX1340 toc10
SAMPLING RATE (ksps)
ANALOG SUPPLY CURRENT (mA)
25020015010050
0.5
1.0
1.5
2.0
2.5
3.0
0
0300
1.90
1.94
1.92
1.98
1.96
2.02
2.00
2.04
ANALOG SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
MAX1340 toc11
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
4.750 4.875 5.000 5.125 5.250
1.88
1.92
1.90
1.96
1.94
2.00
1.98
2.02
-40 10-15 35 60 85
ANALOG SUPPLY CURRENT
vs. TEMPERATURE
MAX1340 toc12
TEMPERATURE (°C)
ANALOG SUPPLY CURRENT (mA)
DAC INTEGRAL NONLINEARITY
vs. OUTPUT CODE
MAX1340 toc13
OUTPUT CODE
INTEGRAL NONLINEARITY (LSB)
307220481024
-1.0
-0.5
0
0.5
1.0
1.5
-1.5
04096
DAC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
MAX1340 toc14
OUTPUT CODE
DIFFERENTIAL NONLINEARITY (LSB)
2059205620532050
-0.2
0
0.2
0.4
-0.4
2047 2062
0.2
0.4
0.8
0.6
1.0
1.2
MAX1340 toc15
SUPPLY VOLTAGE (V)
DAC FULL-SCALE ERROR (LSB)
4.750 5.0004.875 5.125 5.250
DAC FULL-SCALE ERROR
vs. ANALOG SUPPLY
-6
-4
-2
0
2
4
6
8
10
-40 -15 10 35 60 85
DAC FULL-SCALE ERROR
vs. TEMPERATURE
MAX1340 toc16
TEMPERATURE (°C)
DAC FULL-SCALE ERROR (LSB)
INTERNAL REFERENCE
EXTERNAL REFERENCE
DAC FULL-SCALE ERROR
vs. REFERENCE VOLTAGE
MAX1340 toc17
REFERENCE VOLTAGE (V)
DAC FULL-SCALE ERROR (LSB)
431 2
-0.75
-0.50
-0.25
0
0.25
0.50
0.75
1.00
-1.00
05
DAC FULL-SCALE ERROR
vs. LOAD CURRENT
MAX1340 toc18
LOAD CURRENT (mA)
DAC FULL-SCALE ERROR (LSB)
252015105
-10
-5
0
5
-15
030
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
10 ______________________________________________________________________________________
Typical Operating Characteristics (continued)
(AVDD = DVDD = 5V, external VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), fSAMPLE = 225ksps, CLOAD = 50pF, 0.1µF capacitor
at REF, TA= +25°C, unless otherwise noted.)
4.12
4.11
4.10
4.09
4.08
-40 10-15 35 60 85
INTERNAL REFERENCE VOLTAGE
vs. TEMPERATURE
MAX1340 toc19
TEMPERATURE (°C)
INTERNAL REFERENCE VOLTAGE (V)
24.84
24.88
24.86
24.92
24.90
24.94
24.96
4.750 5.0004.875 5.125 5.250
ADC REFERENCE SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
MAX1340 toc20
SUPPLY VOLTAGE (V)
ADC REFERENCE SUPPLY CURRENT (µA)
40.5
40.6
40.8
40.7
40.9
41.0
-40 10-15 35 60 85
ADC REFERENCE SUPPLY CURRENT
vs. TEMPERATURE
MAX1340 toc21
TEMPERATURE (°C)
INTERNAL REFERENCE SUPPLY CURRENT (µA)
ADC FFT PLOT
MAX1340 toc22
ANALOG INPUT FREQUENCY (kHz)
AMPLITUDE (dB)
15010050
-140
-120
-100
-80
-60
-40
-20
0
-160
0 200
fSAMPLE = 32.768kHz
fANALOG_)N = 10.080kHz
fCLK = 5.24288MHz
SINAD = 71.27dBc
SNR = 71.45dBc
THD = 85.32dBc
SFDR = 87.25dBc
ADC IMD PLOT
MAX1340 toc23
ANALOG INPUT FREQUENCY (kHz)
AMPLITUDE (dB)
15010050
-140
-120
-100
-80
-60
-40
-20
0
-160
0 200
fCLK = 5.24288MHz
fIN1 = 9.0kHz
fIN2 = 11.0kHz
AIN = -6dBFS
IMD = 82.99dBc
ADC CROSSTALK PLOT
MAX1340 toc24
ANALOG INPUT FREQUENCY (kHz)
AMPLITUDE (dB)
15010050
-140
-120
-100
-80
-60
-40
-20
0
-160
0 200
fCLK = 5.24288MHz
fIN1 = 10.080kHz
fIN2 = 8.0801kHz
SNR = 72.00dBc
THD = 85.24dBc
ENOB = 11.65 BITS
DAC OUTPUT LOAD REGULATION
vs. OUTPUT CURRENT
MAX1340 toc25
OUTPUT CURRENT (mA)
DAC OUTPUT VOLTAGE (V)
60300
2.01
2.02
2.03
2.04
2.05
2.06
2.07
2.08
2.00
-30 90
DAC OUTPUT = MIDSCALE
SINKING
SOURCING
GPIO OUTPUT VOLTAGE
vs. SOURCE CURRENT
MAX1340 toc26
SOURCE CURRENT (mA)
GPIO OUTPUT VOLTAGE (V)
80604020
1
2
3
4
5
0
0 100
GPIOA0–A3 OUTPUTS
GPIOB0–B3,
C0–C3 OUTPUTS
GPIO OUTPUT VOLTAGE
vs. SINK CURRENT
MAX1340 toc27
SINK CURRENT (mA)
GPIO OUTPUT VOLTAGE (mV)
80604020
300
600
900
1200
1500
0
0 100
GPIOA0–A3 OUTPUTS
GPIOB0–B3, C0–C3
OUTPUTS
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 11
Typical Operating Characteristics (continued)
(AVDD = DVDD = 5V, external VREF = 4.096V, fCLK = 3.6MHz (50% duty cycle), fSAMPLE = 225ksps, CLOAD = 50pF, 0.1µF capacitor
at REF, TA= +25°C, unless otherwise noted.)
TEMPERATURE SENSOR ERROR
vs. TEMPERATURE
MAX1340 toc28
TEMPERATURE (°C)
TEMPERATURE SENSOR ERROR (°C)
6035-15 10
-0.75
-0.50
-0.25
0
0.25
0.50
0.75
1.00
-1.00
-40 85
DAC-TO-DAC CROSSTALK
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc29
100µs
VOUTA
2V/div
VOUTB
10mV/div
AC-COUPLED
DYNAMIC RESPONSE RISE TIME
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc30
1µs
VOUT
2V/div
CS
2V/div
DYNAMIC RESPONSE FALL TIME
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc31
1µs
VOUT
2V/div
CS
2V/div
MAJOR CARRY TRANSITION
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc32
1µs
VOUT
20mV/div
AC-COUPLED
CS
2V/div
DAC DIGITAL FEEDTHROUGH
RLOAD = 10kΩ, CLOAD = 100pF,
CS = HIGH, DIN = LOW
MAX1340 toc33
200ns
VOUT
100mV/div
AC-COUPLED
SCLK
2V/div
NEGATIVE FULL-SCALE SETTLING TIME
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc34
2µs
VOUT_
2V/div
VLDAC
2V/div
POSITIVE FULL-SCALE SETTLING TIME
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc35
1µs
VOUT_
2V/div
VLDAC
2V/div
ADC REFERENCE FEEDTHROUGH
RLOAD = 10kΩ, CLOAD = 100pF
MAX1340 toc36
200µs
VDAC-OUT
2mV/div
AC-COUPLED
VREF2
2V/div
ADC REFERENCE SWITCHING
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
12 ______________________________________________________________________________________
Pin Description
MAX1340
MAX1342 MAX1346 MAX1348
NAME FUNCTION
1, 2, 16–19,
24, 25 16–19
1, 2, 16–19,
24, 25, 31,
34
16–19, 31,
34 D.C. Do Not Connect. Do not connect to this pin.
3333EOC Active-Low End-of-Conversion Output. Data is valid after the
falling edge of EOC.
4444DV
DD Digital Positive Power Input. Bypass DVDD to DGND with a
0.1µF capacitor.
5 5 5 5 DGND Digital Ground. Connect DGND to AGND.
6 6 6 6 DOUT
Serial Data Output. Data is clocked out on the falling edge of
the SCLK clock in clock modes 00, 01, and 10. Data is
clocked out on the rising edge of the SCLK clock in clock
mode 11. High impedance when CS is high.
7 7 7 7 SCLK
Serial Clock Input. Clocks data in and out of the serial
interface. (Duty cycle must be 40% to 60%.) See Table 4 for
details on programming the clock mode.
8888DIN
Serial Data Input. DIN data is latched into the serial interface
on the falling edge of SCLK.
9–12 9–12 9–12 9–12 OUT0–
OUT3 DAC Outputs
13 13 13 13 AVDD Positive Analog Power Input. Bypass AVDD to AGND with a
0.1µF capacitor.
14 14 14 14 AGND Analog Ground
15, 23, 32,
33
15, 23, 32,
33
15, 23, 32,
33
15, 23, 32,
33 N.C. No Connection. Not internally connected.
20 20 20 20 LDAC
Active-Low Load DAC. LDAC is an asynchronous active-low
input that updates the DAC outputs. Drive LDAC low to make
the DAC registers transparent.
21 21 21 21 CS
Active-Low Chip-Select Input. When CS is low, the serial
interface is enabled. When CS is high, DOUT is high
impedance.
22 22 22 22
RES_SEL
Reset Select. Selects DAC wake-up mode. Set RES_SEL low
to wake up the DAC outputs with a 100kΩ resistor to GND or
set RES_SEL high to wake up the DAC outputs with a 100kΩ
resistor to VREF. Set RES_SEL high to power up the DAC input
register to FFFh. Set RES_SEL low to power up the DAC input
register to 000h.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 13
Pin Description (continued)
MAX1340
MAX1342 MAX1346 MAX1348
NAME FUNCTION
26 26 26 26 REF1
Reference 1 Input. Reference voltage. Leave unconnected to
use the internal reference (4.096V). REF1 is the positive
reference in ADC external differential reference mode. Bypass
REF1 to AGND with a 0.1µF capacitor in external reference
mode only. See the ADC/DAC References section.
27–31, 34
27–31, 34
——
AIN0–AIN5
Analog Inputs
35 35 — —
REF2/AIN6
Reference 2 Input/Analog Input Channel 6. See Table 5 for
details on programming the setup register. REF2 is the
negative reference in the ADC external differential reference
mode.
36 36 — — CNVST/
AIN7
Active-Low Conversion Start Input/Analog Input 7. See Table 5
for details on programming the setup register.
— 1, 2 — 1, 2 GPIOA0,
GPIOA1
General-Purpose I/O A0, A1. GPIOA0, GPIOA1 can sink and
source 15mA.
— 24, 25 — 24, 25 GPIOC0,
GPIOC1
General-Purpose I/O C0, C1. GPIOC0, GPIOC1 can sink 4mA
and source 2mA.
— — 27–30 27–30
AIN0–AIN3
Analog Inputs
— — 35 35 REF2
Reference 2 Input. See Table 5 for details on programming the
setup register. REF2 is the negative reference in the ADC
external differential reference mode.
— — 36 36 CNVST Active-Low Conversion Start Input. See Table 5 details on
programming the setup register.
————EP
Exposed Paddle. Must be externally connected to AGND. Do
not use as a ground connect.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
14 ______________________________________________________________________________________
Detailed Description
The MAX1340/MAX1342/MAX1346/MAX1348 integrate
a multichannel 12-bit ADC, and a quad 12-bit DAC in a
single IC. The devices also include a temperature sen-
sor and configurable GPIOs with a 25MHz SPI-/QSPI-
/MICROWIRE-compatible serial interface. The ADC is
available in a 4 or an 8 input-channel version. The four
DAC outputs settle within 2.0µs, and the ADC has a
225ksps conversion rate.
All devices include an internal reference (4.096V) pro-
viding a well-regulated, low-noise reference for both the
ADC and DAC. Programmable reference modes for the
ADC and DAC allow the use of an internal reference, an
external reference, or a combination of both. Features
such as an internal ±1°C accurate temperature sensor,
FIFO, scan modes, programmable internal or external
clock modes, data averaging, and AutoShutdown allow
users to minimize both power consumption and proces-
sor requirements. The low glitch energy (4nV•s) and
low digital feedthrough (0.5nV•s) of the integrated quad
DACs make these devices ideal for digital control of
fast-response closed-loop systems.
The devices are guaranteed to operate with a supply
voltage from +4.75V to +5.25V. The devices consume
2.5mA at 225ksps throughput, only 22µA at 1ksps
throughput, and under 0.2µA in the shutdown mode.
The MAX1342/MAX1348 offer four GPIOs that can be
configured as inputs or outputs.
Figure 1 shows the MAX1342 functional diagram. The
MAX1342/MAX1348 only include the GPIO A0, A1, GPIO
C0, C1 blocks. The MAX1340/MAX1346 exclude the
GPIOs. The output-conditioning circuitry takes the internal
parallel data bus and converts it to a serial data format at
DOUT, with the appropriate wake-up timing. The arith-
metic logic unit (ALU) performs the averaging function.
SPI-Compatible Serial Interface
The MAX1340/MAX1342/MAX1346/MAX1348 feature a
serial interface that is compatible with SPI and
MICROWIRE devices. For SPI, ensure the SPI bus mas-
ter (typically a microcontroller (µC)) runs in master
mode so that it generates the serial clock signal. Select
the SCLK frequency of 25MHz or less, and set the
clock polarity (CPOL) and phase (CPHA) in the µC con-
trol registers to the same value. The MAX1340/
MAX1342/MAX1346/MAX1348 operate with SCLK idling
high or low, and thus operate with CPOL = CPHA = 0 or
CPOL = CPHA = 1. Set CS low to latch any input data
at DIN on the falling edge of SCLK. Output data at
DOUT is updated on the falling edge of SCLK in clock
modes 00, 01, and 10. Output data at DOUT is updated
on the rising edge of SCLK in clock mode 11. See
Figures 6–11. Bipolar true-differential results and tem-
perature-sensor results are available in two’s comple-
ment format, while all other results are in binary.
A high-to-low transition on CS initiates the data-input
operation. Serial communications to the ADC always
begin with an 8-bit command byte (MSB first) loaded
from DIN. The command byte and the subsequent data
bytes are clocked from DIN into the serial interface on
the falling edge of SCLK. The serial-interface and fast-
interface circuitry is common to the ADC, DAC, and
GPIO sections. The content of the command byte
determines whether the SPI port should expect 8, 16, or
24 bits and whether the data is intended for the ADC,
DAC, or GPIOs (if applicable). See Table 1. Driving CS
high resets the serial interface.
The conversion register controls ADC channel selec-
tion, ADC scan mode, and temperature-measurement
requests. See Table 4 for information on writing to the
conversion register. The setup register controls the
clock mode, reference, and unipolar/bipolar ADC con-
figuration. Use a second byte, following the first, to
write to the unipolar-mode or bipolar-mode registers.
See Table 5 for details of the setup register and see
Tables 6, 7, and 8 for setting the unipolar- and bipolar-
mode registers. Hold CS low between the command
byte and the second and third byte. The ADC averag-
ing register is specific to the ADC. See Table 9 to
address that register. Table 11 shows the details of the
reset register.
Begin a write to the DAC by writing 0001XXXX as a
command byte. The last 4 bits of this command byte
are don’t-care bits. Write another 2 bytes (holding CS
low) to the DAC interface register following the com-
mand byte to select the appropriate DAC and the data
to be written to it. See the
DAC Serial Interface
section
and Tables 10, 17, and 18.
Write to the GPIOs (if applicable) by issuing a command
byte to the appropriate register. Writing to the
MAX1342/MAX1348 GPIOs requires 1 additional byte fol-
lowing the command byte. See Tables 12–16 for details
on GPIO configuration, writes, and reads. See the
GPIO
Command
section. Command bytes written to the
GPIOs on devices without GPIOs are ignored.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 15
DOUT
EOC
ADDRESS
AIN0
AIN5
REF2/
AIN6
CNVST/
AIN7
REF1
DIN
SCLK
CS
GPIOA0,
GPIOA1
GPIOC0,
GPIOC1
AVDD
SPI
PORT
GPIO
CONTROL
INPUT
REGISTER
DAC
REGISTER
OUTPUT
CONDITIONING
12-BIT
DAC BUFFER
USER-PROGRAMMABLE
I/O
OSCILLATOR
OUT0
OUT1
OUT2
MAX1342
12-BIT
SAR
ADC
LOGIC
CONTROL
TEMPERATURE
SENSOR
FIFO AND
ALU
LDAC RES_SEL
AGND
T/H
REF2
INPUT
REGISTER
DAC
REGISTER
OUTPUT
CONDITIONING
12-BIT
DAC BUFFER
INPUT
REGISTER
DAC
REGISTER
OUTPUT
CONDITIONING
12-BIT
DAC BUFFER
INPUT
REGISTER
DAC
REGISTER
OUTPUT
CONDITIONING
12-BIT
DAC BUFFER
INTERNAL
REFERENCE
OUT3
DGND
DVDD
CNVST
Figure 1. MAX1342 Functional Diagram
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
16 ______________________________________________________________________________________
Table 1. Command Byte (MSB First)
REGISTER NAME BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
Conversion* 1 X CHSEL2 CHSEL1 CHSEL0 SCAN1 SCAN0 TEMP
Setup 0 1 CKSEL1 CKSEL0 REFSEL1 REFSEL0 DIFFSEL1 DIFFSEL0
ADC Averaging 0 0 1 AVGON NAVG1 NAVG0 NSCAN1 NSCAN0
DAC Select 0 0 0 1 XXXX
Reset 0 0 0 0 1 RESET SLOW FBGON
GPIO Configure** 0 0 000011
GPIO Write** 0 0 000010
GPIO Read** 0 0 000001
No Operation 0 0 000000
X = Don’t care.
*
CHESL2 bit is only valid on the MAX1340/MAX1342. Set CHSEL2 to zero on the MAX1346/MAX1348.
*
*
Only applicable on the MAX1342/MAX1348.
Power-Up Default State
The MAX1340/MAX1342/MAX1346/MAX1348 power up
with all blocks in shutdown (including the reference). All
registers power up in state 00000000, except for the
setup register and the DAC input register. The setup
register powers up at 0010 1000 with CKSEL1 = 1 and
REFSEL1 = 1. The DAC input register powers up to
FFFh when RES_SEL is high and powers up to 000h
when RES_SEL is low.
12-Bit ADC
The MAX1340/MAX1342/MAX1346/MAX1348 ADCs use
a fully differential successive-approximation register
(SAR) conversion technique and on-chip track-and-
hold (T/H) circuitry to convert temperature and voltage
signals into 12-bit digital results. The analog inputs
accept both single-ended and differential input signals.
Single-ended signals are converted using a unipolar
transfer function, and differential signals are converted
using a selectable bipolar or unipolar transfer function.
See the
ADC Transfer Functions
section for more data.
ADC Clock Modes
When addressing the setup, register bits 5 and 4 of the
command byte (CKSEL1 and CKSEL0, respectively)
control the ADC clock modes. See Table 5. Choose
between four different clock modes for various ways to
start a conversion and determine whether the acquisi-
tions are internally or externally timed. Select clock
mode 00 to configure CNVST/AIN_ to act as a conver-
sion start and use it to request internally timed conver-
sions, without tying up the serial bus. In clock mode 01,
use CNVST to request conversions one channel at a
time, thereby controlling the sampling speed without
tying up the serial bus. Request and start internally
timed conversions through the serial interface by writ-
ing to the conversion register in the default clock mode,
10. Use clock mode 11 with SCLK up to 3.6MHz for
externally timed acquisitions to achieve sampling rates
up to 225ksps. Clock mode 11 disables scanning and
averaging. See Figures 6–9 for timing specifications on
how to begin a conversion.
These devices feature an active-low, end-of-conversion
output. EOC goes low when the ADC completes the last
requested operation and is waiting for the next com-
mand byte. EOC goes high when CS or CNVST go low.
EOC is always high in clock mode 11.
Single-Ended or Differential Conversions
The MAX1340/MAX1342/MAX1346/MAX1348 use a fully
differential ADC for all conversions. When a pair of
inputs are connected as a differential pair, each input is
connected to the ADC. When configured in single-
ended mode, the positive input is the single-ended
channel and the negative input is referred to AGND.
See Figure 2.
In differential mode, the T/H samples the difference
between two analog inputs, eliminating common-mode
DC offsets and noise. IN+ and IN- are selected from the
following pairs: AIN0/AIN1, AIN2/AIN3, AIN4/AIN5,
AIN6/AIN7. AIN0–AIN3 are available on all devices.
AIN0–AIN7 are available on the MAX1340/MAX1342.
See Tables 5–8 for more details on configuring the
inputs. For the inputs that are configurable as CNVST,
REF2, and an analog input, only one function can be
used at a time.
Unipolar or Bipolar Conversions
Address the unipolar- and bipolar-mode registers
through the setup register (bits 1 and 0). See Table 5 for
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 17
the setup register. See Figures 3 and 4 for the transfer-
function graphs. Program a pair of analog inputs for dif-
ferential operation by writing a one to the appropriate bit
of the bipolar- or unipolar-mode register. Unipolar mode
sets the differential input range from 0 to VREF1. A nega-
tive differential analog input in unipolar mode causes the
digital output code to be zero. Selecting bipolar mode
sets the differential input range to ±VREF1/2. The digital
output code is binary in unipolar mode and two’s com-
plement in bipolar mode.
In single-ended mode, the MAX1340/MAX1342/
MAX1346/MAX1348 always operate in unipolar mode.
The analog inputs are internally referenced to AGND
with a full-scale input range from 0 to the selected refer-
ence voltage.
Analog Input (T/H)
The equivalent circuit of Figure 2 shows the ADC input
architecture of the MAX1340/MAX1342/MAX1346/
MAX1348. In track mode, a positive input capacitor is
connected to AIN0–AIN7 in single-ended mode and
AIN0, AIN2, AIN4, and AIN6 in differential mode. A neg-
ative input capacitor is connected to AGND in single-
ended mode or AIN1, AIN3, AIN5, and AIN7 in
differential mode. For external T/H timing, use clock
mode 01. After the T/H enters hold mode, the difference
between the sampled positive and negative input volt-
ages is converted. The input capacitance charging rate
determines the time required for the T/H to acquire an
input signal. If the input signal’s source impedance is
high, the required acquisition time lengthens.
Any source impedance below 300Ωdoes not signifi-
cantly affect the ADC’s AC performance. A high-imped-
ance source can be accommodated either by
lengthening tACQ (only in clock mode 01) or by placing
a 1µF capacitor between the positive and negative ana-
log inputs. The combination of the analog-input source
impedance and the capacitance at the analog input cre-
ates an RC filter that limits the analog input bandwidth.
Input Bandwidth
The ADC’s input-tracking circuitry has a 1MHz small-sig-
nal bandwidth, making it is possible to digitize high-
speed transient events and measure periodic signals
with bandwidths exceeding the ADC’s sampling rate by
using undersampling techniques. Anti-alias prefiltering
of the input signals is necessary to avoid high-frequency
signals aliasing into the frequency band of interest.
Analog-Input Protection
Internal electrostatic-discharge (ESD) protection diodes
clamp all analog inputs to AVDD and AGND, allowing
the inputs to swing from (AGND - 0.3V) to (AVDD +
0.3V) without damage. However, for accurate conver-
sions near full scale, the inputs must not exceed AVDD
by more than 50mV or be lower than AGND by 50mV. If
an analog input voltage exceeds the supplies, limit the
input current to 2mA.
Internal FIFO
The MAX1340/MAX1342/MAX1346/MAX1348 contain a
first-in/first-out (FIFO) buffer that holds up to 16 ADC
results plus one temperature result. The internal FIFO
allows the ADC to process and store multiple internally
clocked conversions and a temperature measurement
without being serviced by the serial bus.
If the FIFO is filled and further conversions are request-
ed without reading from the FIFO, the oldest ADC
results are overwritten by the new ADC results. Each
result contains 2 bytes, with the MSB preceded by four
leading zeros. After each falling edge of CS, the oldest
available pair of bytes of data is available at DOUT,
MSB first. When the FIFO is empty, DOUT is zero.
The first 2 bytes of data read out after a temperature
measurement always contain the 12-bit temperature
result, preceded by four leading zeros, MSB first. If
another temperature measurement is performed before
the first temperature result is read out, the old measure-
ment is overwritten by the new result. Temperature
results are in degrees Celsius (two’s complement), at a
resolution of 8 LSB per degree. See the
Temperature
Measurements
section for details on converting the dig-
ital code to a temperature.
AIN0–AIN7
(SINGLE-ENDED),
AIN0, AIN2,
AIN4, AIN6
(DIFFERENTIAL)
COMPARATOR
HOLD
ACQ
ACQ
HOLD
ACQ
HOLD
AVDD / 2
REF1
AGND
CIN+
CIN-
DAC
AGND
(SINGLE-ENDED),
AIN1, AIN3,
AIN5, AIN7
(DIFFERENTIAL)
Figure 2. Equivalent Input Circuit
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
18 ______________________________________________________________________________________
12-Bit DAC
In addition to the 12-bit ADC, the MAX1340/MAX1342/
MAX1346/MAX1348 also include four voltage-output,
12-bit, monotonic DACs with less than 4 LSB integral
nonlinearity error and less than 1 LSB differential nonlin-
earity error. Each DAC has a 2µs settling time and ultra-
low glitch energy (4nV•s). The 12-bit DAC code is
unipolar binary with 1 LSB = VREF / 4096.
DAC Digital Interface
Figure 1 shows the functional diagram of the MAX1342.
The shift register converts a serial 16-bit word to parallel
data for each input register operating with a clock rate
up to 25MHz. The SPI-compatible digital interface to the
shift register consists of CS, SCLK, DIN, and DOUT.
Serial data at DIN is loaded on the falling edge of SCLK.
Pull CS low to begin a write sequence. Begin a write to
the DAC by writing 0001XXXX as a command byte. The
last 4 bits of the DAC select register are don’t-care bits.
See Table 10. Write another 2 bytes to the DAC inter-
face register following the command byte to select the
appropriate DAC and the data to be written to it. See
Tables 17 and 18.
The four double-buffered DACs include an input and a
DAC register. The input registers are directly connect-
ed to the shift register and hold the result of the most
recent write operation. The four 12-bit DAC registers
hold the current output code for the respective DAC.
Data can be transferred from the input registers to the
DAC registers by pulling LDAC low or by writing the
appropriate DAC command sequence at DIN. See
Table 17. The outputs of the DACs are buffered through
four rail-to-rail op amps.
The MAX1340/MAX1342/MAX1346/MAX1348 DAC out-
put-voltage range is based on the internal reference or
an external reference. Write to the setup register (see
Table 5) to program the reference. If using an external
voltage reference, bypass REF1 with a 0.1µF capacitor
to AGND. The internal reference is 4.096V. When using
an external reference, the voltage range is 0.7V to AVDD.
DAC Transfer Function
See Table 2 for various analog outputs from the DAC.
DAC Power-On Wake-Up Modes
The state of the RES_SEL input determines the wake-up
state of the DAC outputs. Connect RES_SEL to AVDD or
AGND upon power-up to be sure the DAC outputs
wake up to a known state. Connect RES_SEL to AGND
to wake up all DAC outputs at 000h. While RES_SEL is
low, the 100kΩinternal resistor pulls the DAC outputs to
AGND and the output buffers are powered down.
Connect RES_SEL to AVDD to wake up all DAC outputs
at FFFh. While RES_SEL is high, the 100kΩpullup
resistor pulls the DAC outputs to VREF1 and the output
buffers are powered down.
DAC Power-Up Modes
See Table 18 for a description of the DAC power-up
and power-down modes.
GPIOs
In addition to the internal ADC and DAC, the
MAX1342/MAX1348 also provide four GPIO channels,
GPIOA0, GPIOA1, GPIOC0, GPIOC1. Read and write to
the GPIOs as detailed in Table 1 and Tables 12–16. Also,
see the
GPIO Command
section. See Figures 11 and 12
for GPIO timing.
Write to the GPIOs by writing a command byte to the
GPIO command register. Write a single data byte to the
MAX1342/MAX1348 following the command byte.
DAC CONTENTS
MSB LSB ANALOG OUTPUT
1111 1111 1111
1000 0000 0001
1000 0000 0000
0111 0111 0111
0000 0000 0001
0000 0000 0000 0
+⎛
⎝
⎜⎞
⎠
⎟
VREF 4095
4096
+⎛
⎝
⎜⎞
⎠
⎟=+
⎛
⎝
⎜⎞
⎠
⎟
VV
REF REF
2048
4096 2
+⎛
⎝
⎜⎞
⎠
⎟
VREF 2047
4096
+⎛
⎝
⎜⎞
⎠
⎟
VREF 1
4096
+⎛
⎝
⎜⎞
⎠
⎟
VREF 2049
4096
Table 2. DAC Output Code Table
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 19
The GPIOs can sink and source current. The
MAX1342/MAX1348 GPIOA0 and GPIOA1 can sink and
source up to 15mA. GPIOC0 and GPIOC1 can sink 4mA
and source 2mA. See Table 3.
Clock Modes
Internal Clock
The MAX1340/MAX1342/MAX1346/MAX1348 can oper-
ate from an internal oscillator. The internal oscillator is
active in clock modes 00, 01, and 10. Figures 6, 7, and
8 show how to start an ADC conversion in the three
internally timed conversion modes.
Read out the data at clock speeds up to 25MHz
through the SPI interface.
External Clock
Set CKSEL1 and CKSEL0 in the setup register to 11 to
set up the interface for external clock mode 11. See
Table 5. Pulse SCLK at speeds from 0.1MHz to
3.6MHz. Write to SCLK with a 40% to 60% duty cycle.
The SCLK frequency controls the conversion timing.
See Figure 9 for clock mode 11 timing. See the
ADC
Conversions in Clock Mode 11
section.
ADC/DAC References
Address the reference through the setup register, bits 3
and 2. See Table 5. Following a wake-up delay, set
REFSEL[1:0] = 00 to program both the ADC and DAC
for internal reference use. Set REFSEL[1:0] = 10 to pro-
gram the ADC for internal reference use without a
wake-up delay. Set REFSEL[1:0] = 10 to program the
DAC for external reference, REF1. When using REF1 or
REF2/AIN_ in external reference, connect a 0.1µF
capacitor to AGND. Set REFSEL[1:0] = 01 to program
the ADC and DAC for external-reference mode. The
DAC uses REF1 as its external reference, while the
ADC uses REF2 as its external reference. Set
REFSEL[1:0] = 11 to program the ADC for external dif-
ferential reference mode. REF1 is the positive reference
and REF2 is the negative reference in the ADC external
differential mode.
When REFSEL[1:0] = 00 or 10, REF2/AIN_ functions as
an analog input channel. When REFSEL[1:0] = 01 or 11,
REF2/AIN_ functions as the device’s negative reference.
Temperature Measurements
Issue a command byte setting bit 0 of the conversion
register to one to take a temperature measurement.
See Table 4. The MAX1340/MAX1342/MAX1346/
MAX1348 perform temperature measurements with an
internal diode-connected transistor. The diode bias cur-
rent changes from 68µA to 4µA to produce a tempera-
ture-dependent bias voltage difference. The second
conversion result at 4µA is subtracted from the first at
68µA to calculate a digital value that is proportional to
absolute temperature. The output data appearing at
DOUT is the digital code above, minus an offset to
adjust from Kelvin to Celsius.
The reference voltage used for the temperature mea-
surements is always derived from the internal reference
source to ensure that 1 LSB corresponds to 1/8 of a
degree Celsius. On every scan where a temperature
measurement is requested, the temperature conversion
is carried out first. The first 2 bytes of data read from
the FIFO contain the result of the temperature measure-
ment. If another temperature measurement is per-
formed before the first temperature result is read out,
the old measurement is overwritten by the new result.
Temperature results are in degrees Celsius (two’s com-
plement). See the
Applications Information
section for
information on how to perform temperature measure-
ments in each clock mode.
Register Descriptions
The MAX1340/MAX1342/MAX1346/MAX1348 communi-
cate between the internal registers and the external cir-
cuitry through the SPI-compatible serial interface. Table
1 details the command byte, the registers, and the bit
names. Tables 4–12 show the various functions within
the conversion register, setup register, unipolar-mode
register, bipolar-mode register, ADC averaging regis-
ter, DAC select register, reset register, and GPIO com-
mand register, respectively.
Conversion Register
Select active analog input channels, scan modes, and a
single temperature measurement per scan by issuing a
command byte to the conversion register. Table 4
details channel selection, the four scan modes, and how
to request a temperature measurement. Start a scan by
writing to the conversion register when in clock mode 10
or 11, or by applying a low pulse to the CNVST pin when
in clock mode 00 or 01. See Figures 6 and 7 for timing
specifications for starting a scan with CNVST.
MAX1342/MAX1348
CURRENT GPIOA0, GPIOA1
(mA)
GPIOC0, GPIOC1
(mA)
Sink 15 4
Source 15 2
Table 3. GPIO Maximum Sink/Source
Current
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
20 ______________________________________________________________________________________
A conversion is not performed if it is requested on a
channel or one of the channel pairs that has been con-
figured as CNVST or REF2. For channels configured as
differential pairs, the CHSEL0 bit is ignored and the two
pins are treated as a single differential channel. For the
MAX1346/MAX1348, the CHSEL2 bit must be zero.
Channels 4–7 are invalid. Any scans or averages on
these channels can cause corrupt data.
Select scan mode 00 or 01 to return one result per sin-
gle-ended channel and one result per differential pair
within the selected scanning range (set by bits 2 and 1,
SCAN1 and SCAN0), plus one temperature result if
selected. Select scan mode 10 to scan a single input
channel numerous times, depending on NSCAN1 and
NSCAN0 in the ADC averaging register (Table 9).
Select scan mode 11 to return only one result from a
single channel.
Setup Register
Issue a command byte to the setup register to config-
ure the clock, reference, power-down modes, and ADC
single-ended/differential modes. Table 5 details the bits
in the setup-register command byte. Bits 5 and 4
(CKSEL1 and CKSEL0) control the clock mode, acqui-
sition and sampling, and the conversion start. Bits 3
and 2 (REFSEL1 and REFSEL0) set the device for either
internal or external reference. Bits 1 and 0 (DIFFSEL1
and DIFFSEL0) address the ADC unipolar-mode and
bipolar-mode registers and configure the analog-input
channels for differential operation.
The ADC reference is always on if any of the following
conditions are true:
1) The FBGON bit is set to one in the reset register.
2) At least one DAC output is powered up and
REFSEL[1:0] (in the setup register) = 00.
3) At least one DAC is powered down through the
100kΩto VREF and REFSEL[1:0] = 00.
If any of the above conditions exist, the ADC reference is
always on, but there is a 188 clock-cycle delay before
temperature-sensor measurements begin, if requested.
Table 4. Conversion Register*
BIT
NAME BIT FUNCTION
— 7 (MSB) S et to one to sel ect conver si on r eg i ster .
X 6 Don’t care.
CHSEL2 5
Analog-input channel select
(MAX1340/MAX1342). Set to 0 on
MAX1346/MAX1348.
CHSEL1 4 Analog-input channel select.
CHSEL0 3 Analog-input channel select.
SCAN1 2 Scan-mode select.
SCAN0 1 Scan-mode select.
TEMP 0 (LSB)
Set to one to take a single temp-
erature measurement. The first
conversion result of a scan contains
temperature information.
CHSEL2** CHSEL1 CHSEL0
SELEC T ED
C H AN N EL
( N )
0 0 0 AIN0
0 0 1 AIN1
0 1 0 AIN2
0 1 1 AIN3
1 0 0 AIN4
1 0 1 AIN5
1 1 0 AIN6
1 1 1 AIN7
SCAN1 SCAN0
SCAN MODE
(CHANNEL N IS SELECTED BY
BITS CHSEL2, CHSEL1, AND CHSEL0)
0 0 Scans channels 0 through N.
01
Scans channels N through the highest
numbered channel.
10
S cans channel N r epeated l y. The AD C
aver ag ing reg i ster sets the numb er of
r esul ts.
11N o scan. C onver ts channel N once onl y.
*
See below for bit details.
**
Channels 4–7 are invalid on the MAX1346/MAX1348. Set
CHSEL2 bit to 0 on those devices.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 21
Table 5. Setup Register*
BIT NAME BIT FUNCTION
— 7 (MSB) Set to zero to select setup register.
— 6 Set to one to select setup register.
CKSEL1 5 Clock mode and CNVST configuration; resets to one at power-up.
CKSEL0 4 Clock mode and CNVST configuration.
REFSEL1 3 Reference-mode configuration.
REFSEL0 2 Reference-mode configuration.
DIFFSEL1 1 Unipolar-/bipolar-mode register configuration for differential mode.
DIFFSEL0 0 (LSB) Unipolar-/bipolar-mode register configuration for differential mode.
Table 5a. Clock Modes (see the
Clock Modes
section)
CKSEL1 CKSEL0 CONVERSION CLOCK ACQUISITION/SAMPLING CNVST CONFIGURATION
0 0 Internal Internally timed. CNVST
0 1 Internal Externally timed by CNVST.CNVST
1 0 Internal Internally timed. AIN7
1 1 External (3.6MHz max) Externally timed by SCLK. AIN7
Table 5b. Clock Modes 00, 01, and 10
REFSEL1 REFSEL0 VOLTAGE
REFERENCE
OVERRIDE
CONDITIONS AUTOSHUTDOWN REF2
CONFIGURATION
AIN
Inter nal r efer ence tur ns off after scan i s com p l ete. If
i nter nal r efer ence i s tur ned off, ther e i s a p r og r am m ed
d el ay of 218 i nter nal - conver si on cl ock cycl es.
00
Internal (DAC
and ADC)
Temperature
Internal reference required. There is a programmed
delay of 244 internal-conversion clock cycles for the
internal reference to settle after wake-up.
AIN6
AIN Internal reference not used.
01
External single-
ended (REF1
for DAC and
REF2 for ADC)
Temperature
Internal reference required. There is a programmed
delay of 244 internal-conversion clock cycles for the
internal reference to settle after wake-up.
REF2
AIN
Default reference mode. Internal reference turns off
after scan is complete. If internal reference is turned
off, there is a programmed delay of 218 internal-
conversion clock cycles.
10
Internal (ADC)
and external
REF1 (DAC)
Temperature
Internal reference required. There is a programmed
delay of 244 internal-conversion clock cycles for the
internal reference to settle after wake-up.
AIN6
AIN Internal reference not used.
11
External
differential
(ADC), external
REF1 (DAC)
Temperature
Internal reference required. There is a programmed
delay of 244 internal-conversion clock cycles for the
internal reference to settle after wake-up.
REF2
*
See below for bit details.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
22 ______________________________________________________________________________________
Table 5c. Clock Mode 11
REFSEL1 REFSEL0 VOLTAGE
REFERENCE
OVERRIDE
CONDITIONS AUTOSHUTDOWN REF2
CONFIGURATION
AIN
Inter nal r efer ence tur ns off after scan i s com p l ete. If
i nter nal r efer ence i s tur ned off, ther e i s a p r og r am m ed
d el ay of 218 exter nal - conver si on cl ock cycl es.
00
Internal (DAC
and ADC)
Temperature
Inter nal r efer ence r eq ui r ed . Ther e i s a p r og r am m ed
d el ay of 244 exter nal - conver si on cl ock cycl es for the
i nter nal r efer ence. Tem p er atur e- sensor outp ut ap p ear s
at D OU T after 188 fur ther exter nal cl ock cycl es.
AIN6
AIN Internal reference not used.
01
External single-
ended (REF1
for DAC and
REF2 for ADC)
Tem p er atur e
Inter nal r efer ence r eq ui r ed . Ther e i s a p r og r am m ed
d el ay of 244 exter nal - conver si on cl ock cycl es for the
i nter nal r efer ence. Tem p er atur e- sensor outp ut ap p ear s
at D OU T after 188 fur ther exter nal cl ock cycl es.
REF2
AIN
Default reference mode. Internal reference turns off
after scan is complete. If internal reference is turned
off, there is a programmed delay of 218 external-
conversion clock cycles.
10
Internal (ADC)
and external
REF1 (DAC)
Temperature
Inter nal r efer ence r eq ui r ed . Ther e i s a p r og r am m ed
d el ay of 244 exter nal - conver si on cl ock cycl es for the
i nter nal r efer ence. Tem p er atur e- sensor outp ut ap p ear s
at D OU T after 188 fur ther exter nal cl ock cycl es.
AIN6
AIN Internal reference not used.
11
External
differential
(ADC), external
REF1 (DAC)
Temperature
Inter nal r efer ence r eq ui r ed . Ther e i s a p r og r am m ed
d el ay of 244 exter nal - conver si on cl ock cycl es for the
i nter nal r efer ence. Tem p er atur e- sensor outp ut ap p ear s
at D OU T after 188 fur ther exter nal cl ock cycl es.
REF2
Table 5d. Differential Select Modes
DIFFSEL1 DIFFSEL0 FUNCTION
0 0 No data follows the command setup byte. Unipolar-mode and bipolar-mode registers remain unchanged.
0 1 No data follows the command setup byte. Unipolar-mode and bipolar-mode registers remain unchanged.
1 0 1 byte of data follows the command setup byte and is written to the unipolar-mode register.
1 1 1 byte of data follows the command setup byte and is written to the bipolar-mode register.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 23
Table 6. Unipolar-Mode Register (Addressed Through the Setup Register)
BIT NAME BIT FUNCTION
UCH0/1 7 (MSB) Configure AIN0 and AIN1 for unipolar differential conversion.
UCH2/3 6 Configure AIN2 and AIN3 for unipolar differential conversion.
UCH4/5 5 Configure AIN4 and AIN5 for unipolar differential conversion (MAX1340/MAX1342). Set UCH4/5 to
zero on the MAX1346/MAX1348.
UCH6/7 4 Configure AIN6 and AIN7 for unipolar differential conversion (MAX1340/MAX1342). Set UCH6/7 to
zero on the MAX1346/MAX1348.
X 3 Don’t care.
X 2 Don’t care.
X 1 Don’t care.
X 0 (LSB) Don’t care.
Table 7. Bipolar-Mode Register (Addressed Through the Setup Register)
BIT NAME BIT FUNCTION
BCH0/1 7 (MSB)
Set to one to configure AIN0 and AIN1 for bipolar differential conversion. Set the corresponding bits
in the unipolar-mode and bipolar-mode registers to zero to configure AIN0 and AIN1 for unipolar
single-ended conversion.
BCH2/3 6
Set to one to configure AIN2 and AIN3 for bipolar differential conversion. Set the corresponding bits
in the unipolar-mode and bipolar-mode registers to zero to configure AIN2 and AIN3 for unipolar
single-ended conversion.
BCH4/5 5
Set to one to configure AIN4 and AIN5 for bipolar differential conversion (MAX1340/MAX1342). Set
the corresponding bits in the unipolar-mode and bipolar-mode registers to zero to configure AIN4
and AIN5 for unipolar single-ended conversion. Set BCH4/5 to 0 on the MAX1346/MAX1348.
BCH6/7 4
Set to one to configure AIN6 and AIN7 for bipolar differential conversion (MAX1340/MAX1342). Set
the corresponding bits in the unipolar-mode and bipolar-mode registers to zero to configure AIN6
and AIN7 for unipolar single-ended conversion. Set BCH6/7 to 0 on the MAX1346/MAX1348.
X 3 Don’t care.
X 2 Don’t care.
X 1 Don’t care.
X 0 (LSB) Don’t care.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
24 ______________________________________________________________________________________
Unipolar/Bipolar Registers
The final 2 bits (LSBs) of the setup register control the
unipolar-/bipolar-mode address registers. Set
DIFFSEL[1:0] = 10 to write to the unipolar-mode regis-
ter. Set bits DIFFSEL[1:0] = 11 to write to the bipolar-
mode register. In both cases, the setup command byte
must be followed by 1 byte of data that is written to the
unipolar-mode register or bipolar-mode register. Hold
CS low and run 16 SCLK cycles before pulling CS high.
If the last 2 bits of the setup register are 00 or 01, nei-
ther the unipolar-mode register nor the bipolar-mode
register is written. Any subsequent byte is recognized
as a new command byte. See Tables 6, 7, and 8 to pro-
gram the unipolar- and bipolar-mode registers.
Both registers power up at all zeros to set the inputs as
eight unipolar single-ended channels. To configure a
channel pair as single-ended unipolar, bipolar differen-
tial, or unipolar differential, see Table 8.
In unipolar mode, AIN+ can exceed AIN- by up to
VREF. The output format in unipolar mode is binary. In
bipolar mode, either input can exceed the other by up
to VREF/2. The output format in bipolar mode is two’s
complement (see the
ADC Transfer Functions
section).
ADC Averaging Register
Write a command byte to the ADC averaging register to
configure the ADC to average up to 32 samples for
each requested result, and to independently control the
number of results requested for single-channel scans.
Table 8. Unipolar/Bipolar Channel Function
UNIPOLAR-
MODE
REGISTER BIT
BIPOLAR-MODE
REGISTER BIT
CHANNEL PAIR
FUNCTION
0 0 Unipolar single-ended
0 1 Bipolar differential
1 0 Unipolar differential
1 1 Unipolar differential
Table 9. ADC Averaging Register*
BIT NAME BIT FUNCTION
— 7 (MSB) Set to zero to select ADC averaging register.
— 6 Set to zero to select ADC averaging register.
— 5 Set to one to select ADC averaging register.
AVGON 4 Set to one to turn averaging on. Set to zero to turn averaging off.
NAVG1 3 Configures the number of conversions for single-channel scans.
NAVG0 2 Configures the number of conversions for single-channel scans.
NSCAN1 1 Single-channel scan count. (Scan mode 10 only.)
NSCAN0 0 (LSB) Single-channel scan count. (Scan mode 10 only.)
AVGON NAVG1 NAVG0 FUNCTION
0 X X Performs one conversion for each requested result.
1 0 0 Performs four conversions and returns the average for each requested result.
1 0 1 Performs eight conversions and returns the average for each requested result.
1 1 0 Performs 16 conversions and returns the average for each requested result.
1 1 1 Performs 32 conversions and returns the average for each requested result.
NSCAN1 NSCAN0 FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED)
0 0 Scans channel N and returns four results.
0 1 Scans channel N and returns eight results.
1 0 Scans channel N and returns 12 results.
1 1 Scans channel N and returns 16 results.
*
See below for bit details.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 25
Table 9 details the four scan modes available in the
ADC conversion register. All four scan modes allow
averaging as long as the AVGON bit, bit 4 in the
averaging register, is set to 1. Select scan mode 10 to
scan the same channel multiple times. Clock mode 11
disables averaging. For example, if AVGON = 1,
NAVG[1:0] = 00, NSCAN[1:0] = 11, and SCAN[1:0] =
10, 16 results are written to the FIFO, with each result
being the average of four conversions of channel N.
DAC Select Register
Write a command byte 0001XXXX to the DAC select
register (as shown in Table 9) to set up the DAC inter-
face and indicate that another word will follow. The last
4 bits of the DAC select register are don’t-care bits. The
word that follows the DAC select-register command
byte controls the DAC serial interface. See Table 17
and the
DAC Serial Interface
section.
Reset Register
Write to the reset register (as shown in Table 11) to
clear the FIFO or reset all registers (excluding the DAC
and GPIO registers) to their default states. When the
RESET bit in the reset register is set to 0, the FIFO is
cleared. Set the RESET bit to one to return all the
device registers to their default power-up state. All reg-
isters power up in state 00000000, except for the setup
register that powers up in clock mode 10 (CKSEL1 = 1
and REFSEL1 = 1). The DAC and GPIO registers are
not reset by writing to the reset register. Set the SLOW
bit to one to add a 15ns delay in the DOUT signal path
to provide a longer hold time. Writing a one to the
SLOW bit also clears the contents of the FIFO. Set the
FBGON bit to one to force the bias block and bandgap
reference to power up regardless of the state of the
DAC and activity of the ADC block. Setting the FBGON
bit high also removes the programmed wake-up delay
between conversions in clock modes 01 and 11.
Setting the FBGON bit high also clears the FIFO.
GPIO Command
Write a command byte to the GPIO command register
to configure, write, or read the GPIOs, as detailed in
Table 12.
Write the command byte 00000011 to configure the
GPIOs. The eight SCLK cycles following the command
Table 10. DAC Select Register
BIT
NAME BIT FUNCTION
— 7 (MSB) Set to zero to select DAC select register.
— 6 Set to zero to select DAC select register.
— 5 Set to zero to select DAC select register.
— 4 Set to one to select DAC select register.
X 3 Don’t care.
X 2 Don’t care.
X 1 Don’t care.
X 0 Don’t care.
Table 11. Reset Register
BIT
NAME BIT FUNCTION
— 7 (MSB) Set to zero to select ADC reset register.
— 6 Set to zero to select ADC reset register.
— 5 Set to zero to select ADC reset register.
— 4 Set to zero to select ADC reset register.
— 3 Set to one to select ADC reset register.
RESET 2
Set to zero to clear the FIFO only. Set to
one to set the device in its power-on
condition.
SLOW 1 Set to one to turn on slow mode.
FBGON 0 (LSB)
Set to one to force internal bias block and
bandgap reference to be always powered
up.
Table 12. GPIO Command Register
BIT NAME BIT FUNCTION
— 7 (MSB) Set to zero to select GPIO register.
— 6 Set to zero to select GPIO register.
— 5 Set to zero to select GPIO register.
— 4 Set to zero to select GPIO register.
— 3 Set to zero to select GPIO register.
— 2 Set to zero to select GPIO register.
GPIOSEL1 1 GPIO configuration bit.
GPIOSEL2 0 (LSB) GPIO write bit.
GPIOSEL1 GPIOSEL2 FUNCTION
11
GPIO configuration; written data is
entered in the GPIO configuration
register.
10
GPIO write; written data is entered
in the GPIO write register.
01
GPIO read; the next 8 SCLK cycles
transfer the state of all GPIO
drivers into DOUT.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
26 ______________________________________________________________________________________
Table 13. MAX1342/MAX1348 GPIO Configuration
DATA PIN GPIO COMMAND BYTE DATA BYTE
DIN 0 0 0 0 0 0 1 1 GPIOC1 GPIOC0 GPIOA1 GPIOA0 X X X X
DOUT 00000000 0 0 0 0 0000
Table 14. MAX1342/MAX1348 GPIO Write
DATA PIN GPIO COMMAND BYTE DATA BYTE
DIN 0 0 0 0 0 0 1 0 GPIOC1 GPIOC0 GPIOA1 GPIOA0 X X X X
DOUT 00000000 0 0 0 0 0 0 0 0
byte load data from DIN to the GPIO configuration reg-
ister in the MAX1342/MAX1348. See Tables 13 and 14.
The register bits are updated after the last CS rising
edge. All GPIOs default to inputs upon power-up.
The data in the register controls the function of each
GPIO, as shown in Tables 13, 14, and 16.
GPIO Write
Write the command byte 00000010 to indicate a GPIO
write operation. The eight SCLK cycles following the
command byte load data from DIN into the GPIO write
register in the MAX1342/MAX1348. See Tables 14
and 15. The register bits are updated after the last CS
rising edge.
GPIO Read
Write the command byte 00000001 to indicate a GPIO
read operation. The eight SCLK cycles following the
command byte transfer the state of the GPIOs to DOUT
in the MAX1342/MAX1348. See Table 16.
DAC Serial Interface
Write a command byte 0001XXXX to the DAC select
register to indicate the word to follow is written to the
DAC serial interface, as detailed in Tables 1, 10, 17, and
18. Write the next 16 bits to the DAC interface register,
as shown in Tables 17 and 18. Following the high-to-low
transition of CS, the data is shifted synchronously and
latched into the input register on each falling edge of
SCLK. Each word is 16 bits. The first 4 bits are the con-
trol bits followed by 12 data bits (MSB first). See Figures
9–12 for DAC timing specifications.
If CS goes high prior to completing 16 SCLK cycles, the
command is discarded. To initiate a new transfer, drive
CS low again.
For example, writing the DAC serial interface word 1111
0000 and 0011 0100 disconnects DAC outputs 2 and 3
and forces them to a high-impedance state. DAC out-
puts 0 and 1 remain in their previous state.
Table 15. GPIO-Mode Control
CONFIGURATION
BIT
WRITE
BIT
OUTPUT
STATE
GPIO
FUNCTION
1 1 1 Output
1 0 0 Output
0 1 Tri-state Input
000
Pulldown
(open drain)
Table 16. MAX1342/MAX1348 GPIO Read
DATA PIN GPIO COMMAND BYTE DATA BYTE
DIN 00000001 X X X X X X X X
DOUT 00000000 0 0 0 0 GPIOC1 GPIOC0 GPIOA1 GPIOA0
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 27
Table 17. DAC Serial-Interface Configuration
16-BIT SERIAL WORD
MSB LSB
CONTROL
BITS DATA BITS
C3 C2 C1 C0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
DESCRIPTION FUNCTION
0 0 0 0 X X X X X X X X X X X X NOP No operation.
0 0 0 1 0 X X X X X X X X X X X RESET Reset all internal registers to 000h and
leave output buffers in their present state.
0 0 0 1 1 X X X X X X X X X X X Pull-High Preset all internal registers to FFFh and
leave output buffers in their present state.
0 0 1 0 — — — — — — — — — — — — DAC0 D11–D0 to input register 0,
DAC output unchanged.
0 0 1 1 — — — — — — — — — — — — DAC1 D11–D0 to input register 1,
DAC output unchanged.
0 1 0 0 — — — — — — — — — — — — DAC2 D11–D0 to input register 2,
DAC output unchanged.
0 1 0 1 — — — — — — — — — — — — DAC3 D11–D0 to input register 3,
DAC output unchanged.
0 1 1 0 X X X X X X X X X X X X NOP No operation.
0 1 1 1 X X X X X X X X X X X X NOP No operation.
1 0 0 0 X X X X X X X X X X X X NOP No operation.
1 0 0 1 X X X X X X X X X X X X NOP No operation.
1 0 1 0 — — — — — — — — — — — — DAC0–DAC3
D11–D0 to input registers 0–3 and DAC
registers 1–4. DAC outputs updated
(write-through).
1 0 1 1 X X X X X X X X X X X X NOP No operation.
1 1 0 0 — — — — — — — — — — — — DAC0–DAC3
D11–D0 to input registers 0–3 and DAC
registers 1–4. DAC outputs updated
(write-through).
1 1 0 1 — — — — — — — — — — — — DAC0–DAC3 D11–D0 to input registers 0–3.
DAC outputs unchanged.
1110XXXX
DAC3
DAC2
DAC1
DAC0
X X X X DAC0–DAC3
Input registers to DAC registers indicated
by ones, DAC outputs updated,
equivalent to software LDAC.
(No effect on DACs indicated by zeros.)
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
28 ______________________________________________________________________________________
Output-Data Format
Figures 6–9 illustrate the conversion timing for the
MAX1340/MAX1342/MAX1346/MAX1348. All 12-bit con-
version results are output in 2-byte format, MSB first,
with four leading zeros. Data appears on DOUT on the
falling edges of SCLK. Data is binary for unipolar mode
and two’s complement for bipolar mode and tempera-
ture results. See Figures 3, 4, and 5 for input/output and
temperature-transfer functions.
ADC Transfer Functions
Figure 3 shows the unipolar transfer function for single-
ended or differential inputs. Figure 4 shows the bipolar
transfer function for differential inputs. Code transitions
occur halfway between successive-integer LSB values.
Output coding is binary, with 1 LSB = VREF1 / 4096 for
unipolar and bipolar operation, and 1 LSB = +0.125°C
for temperature measurements. Bipolar true-differential
results and temperature-sensor results are available in
two’s complement format, while all others are in binary.
See Tables 6, 7, and 8 for details on which setting
(unipolar or bipolar) takes precedence.
In unipolar mode, AIN+ can exceed AIN- by up to
VREF1. In bipolar mode, either input can exceed the
other by up to VREF1/2.
Table 18. DAC Power-Up and Power-Down Commands
CONTROL
BITS DATA BITS
C3 C2 C1 C0 X X X X
DAC3
DAC2
DAC1
DAC0
D3 D2 D1 D0
DESCRIPTION FUNCTION
1 1 1 1 X X X X ————0 0 1 X Power-Up
Power up individual DAC buffers indicated by data
in DAC0 through DAC3. A one indicates the DAC
output is connected and active. A zero does not
affect the DAC’s present state.
1 1 1 1 X X X X ————0 1 0 X Power-Down 1
Power down individual DAC buffers indicated by
data in DAC0 through DAC3. A one indicates the
DAC output is disconnected and high impedance.
A zero does not affect the DAC’s present state.
1 1 1 1 X X X X ————1 0 0 X Power-Down 2
Power down individual DAC buffers indicated by
data in DAC0 through DAC3. A one indicates the
DAC output is disconnected and pulled to AGND
with a 1kΩ resistor. A zero does not affect the DAC’s
present state.
1 1 1 1 X X X X ————0 0 0 X Power-Down 3
Power down individual DAC buffers indicated by
data in DAC0 through DAC3. A one indicates the
DAC output is disconnected and pulled to AGND
with a 100kΩ resistor. A zero does not affect the
DAC’s present state.
1 1 1 1 X X X X ————1 1 1 X Power-Down 4
Power down individual DAC buffers indicated by
data in DAC0 through DAC3. A one indicates the
DAC output is disconnected and pulled to REF1 with
a 100kΩ resistor. A zero does not affect the DAC’s
present state.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 29
Partial Reads and Partial Writes
If the first byte of an entry in the FIFO is partially read
(CS is pulled high after fewer than eight SCLK cycles),
the remaining bits are lost for that byte. The next byte of
data that is read out contains the next 8 bits. If the first
byte of an entry in the FIFO is read out fully, but the
second byte is read out partially, the rest of that byte is
lost. The remaining data in the FIFO is unaffected and
can be read out normally after taking CS low again, as
long as the 4 leading bits (normally zeros) are ignored.
If CS is pulled low before EOC goes low, a conversion
may not be completed and the FIFO data may not be
correct. Incorrect writes (pulling CS high before com-
pleting eight SCLK cycles) are ignored and the register
remains unchanged.
Applications Information
Internally Timed Acquisitions and
Conversions Using
CNVST
ADC Conversions in Clock Mode 00
In clock mode 00, the wake-up, acquisition, conversion,
and shutdown sequence is initiated through CNVST
and performed automatically using the internal oscilla-
tor. Results are added to the internal FIFO to be read
out later. See Figure 6 for clock mode 00 timing after a
command byte is issued. See Table 5 for details on
programming the clock mode in the setup register.
Initiate a scan by setting CNVST low for at least 40ns
before pulling it high again. The MAX1340/MAX1342/
MAX1346/MAX1348 then wake up, scan all requested
channels, store the results in the FIFO, and shut down.
After the scan is complete, EOC is pulled low and the
results are available in the FIFO. Wait until EOC goes
low before pulling CS low to communicate with the seri-
al interface. EOC stays low until CS or CNVST is pulled
low again. A temperature-conversion result, if request-
ed, precedes all other FIFO results.
FULL-SCALE
TRANSITION
111....111
0
INPUT VOLTAGE (LSB)
FS = VREF
111....110
111....101
OFFSET BINARY OUTPUT CODE (LSB)
000....011
000....010
000....001
000....000
213 FS
1 LSB = VREF / 4096
FS - 3/2 LSB
Figure 3. Unipolar Transfer Function—Full Scale (FS) = VREF
OUTPUT CODE
011....111
TEMPERATURE (°C)
011....110
000....001
111....101
100....001
100....000
111....111
111....110
000....000
0
000....010
-256 +255.5
Figure 5. Temperature Transfer Function
011....111
-FS
INPUT VOLTAGE (LSB)
FS = VREF / 2 + VCOM
VREF = VREF+ - VREF-
-FS = -VREF / 2
011....110
011....101
000....001
000....000
111....111
OFFSET BINARY OUTPUT CODE (LSB)
100....011
100....010
100....001
100....000
0
(COM)
-1 +1 +FS - 1 LSB
1 LSB = VREF / 4096
ZS = COM
VREF VREF
VREF
(COM)
VREF
Figure 4. Bipolar Transfer Function—Full Scale (±FS) = ±VREF / 2
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
30 ______________________________________________________________________________________
Do not issue a second CNVST signal before EOC goes
low; otherwise, the FIFO can be corrupted. Wait until all
conversions are complete before reading the FIFO. SPI
communications to the DAC and GPIO registers are per-
mitted during conversion. However, coupled noise may
result in degraded ADC signal-to-noise ratio (SNR).
Externally Timed Acquisitions and
Internally Timed Conversions with
CNVST
ADC Conversions in Clock Mode 01
In clock mode 01, conversions are requested one at a
time using CNVST and performed automatically using
the internal oscillator. See Figure 7 for clock mode 01
timing after a command byte is issued.
Setting CNVST low begins an acquisition, wakes up the
ADC, and places it in track mode. Hold CNVST low for
at least 1.4µs to complete the acquisition. If reference
mode 00 or 10 is selected, an additional 45µs is
required for the internal reference to power up. If a tem-
perature measurement is being requested, reference
power-up and temperature measurement is internally
timed. In this case, hold CNVST low for at least 40ns.
Set CNVST high to begin a conversion. Sampling is
completed approximately 500ns after CNVST goes high.
After the conversion is complete, the ADC shuts down
and pulls EOC low. EOC stays low until CS or CNVST is
pulled low again. Wait until EOC goes low before pulling
CS or CNVST low. The number of CNVST signals must
equal the number of conversions requested by the scan
(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)
CS
DOUT
MSB1
tRDS
LSB1 MSB2
SCLK
CNVST
EOC
Figure 6. Clock Mode 00—After writing a command byte, set CNVST low for at least 40ns to begin a conversion.
(CONVERSION 2)
tCSW
tDOV
(ACQUISITION 2)
(ACQUISITION 1)
(CONVERSION 1)
CS
DOUT
MSB1 LSB1 MSB2
SCLK
CNVST
EOC
Figure 7. Clock Mode 01—After writing a command byte, request multiple conversions by setting CNVST low for each conversion.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 31
(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)
MSB1
tDOV
LSB1 MSB2
(CONVERSION BYTE)
CS
DOUT
SCLK
DIN
EOC
Figure 8. Clock Mode 10—The command byte to the conversion register begins the acquisition (CNVST is not required).
and averaging registers to correctly update the FIFO.
Wait until all conversions are complete before reading
the FIFO. SPI communications to the DAC and GPIO
registers are permitted during conversion. However,
coupled noise may result in degraded ADC SNR.
If averaging is turned on, multiple CNVST pulses need to
be performed before a result is written to the FIFO. Once
the proper number of conversions has been performed
to generate an averaged FIFO result (as specified to the
averaging register), the scan logic automatically switch-
es the analog-input multiplexer to the next requested
channel. If a temperature measurement is programmed,
it is performed after the first rising edge of CNVST follow-
ing the command byte written to the conversion register.
The temperature-conversion result is available on DOUT
once EOC has been pulled low.
Internally Timed Acquisitions and
Conversions Using the Serial Interface
ADC Conversions in Clock Mode 10
In clock mode 10, the wake-up, acquisition, conversion,
and shutdown sequence is initiated by writing a com-
mand byte to the conversion register, and is performed
automatically using the internal oscillator. This is the
default clock mode upon power-up. See Figure 8 for
clock mode 10 timing.
Initiate a scan by writing a command byte to the conver-
sion register. The MAX1340/MAX1342/MAX1346/
MAX1348 then power up, scan all requested channels,
store the results in the FIFO, and shut down. After the
scan is complete, EOC is pulled low and the results are
available in the FIFO. If a temperature measurement is
requested, the temperature result precedes all other
FIFO results. EOC stays low until CS is pulled low again.
Wait until all conversions are complete before reading
the FIFO. SPI communications to the DAC and GPIO
registers are permitted during conversion. However,
coupled noise may result in degraded ADC SNR.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
32 ______________________________________________________________________________________
Externally Clocked Acquisitions and
Conversions Using the Serial Interface
ADC Conversions in Clock Mode 11
In clock mode 11, acquisitions and conversions are ini-
tiated by writing a command byte to the conversion
register and are performed one at a time using the
SCLK as the conversion clock. Scanning, averaging
and the FIFO are disabled, and the conversion result is
available at DOUT during the conversion. Output data
is updated on the rising edge of SCLK in clock mode
11. See Figure 9 for clock mode 11 timing.
Initiate a conversion by writing a command byte to the
conversion register followed by 16 SCLK cycles. If CS
is pulsed high between the eighth and ninth cycles, the
pulse width must be less than 100µs. To continuously
convert at 16 cycles per conversion, alternate 1 byte of
zeros (NOP byte) between each conversion byte. If 2
NOP bytes follow a conversion byte, the analog cells
power down at the end of the second NOP. Set the
FBGON bit to one in the reset register to keep the inter-
nal bias block powered.
If reference mode 00 is requested, or if an external refer-
ence is selected but a temperature measurement is being
requested, wait 45µs with CS high after writing the con-
version byte to extend the acquisition and allow the inter-
nal reference to power up. To perform a temperature
measurement, write 24 bytes (192 cycles) of zeros after
the conversion byte. The temperature result appears on
DOUT during the last 2 bytes of the 192 cycles.
Conversion-Time Calculations
The conversion time for each scan is based on a num-
ber of different factors: conversion time per sample,
samples per result, results per scan, if a temperature
measurement is requested, and if the external refer-
ence is in use. Use the following formula to calculate
the total conversion time for an internally timed conver-
sion in clock mode 00 and 10 (see the
Electrical
Characteristics
, as applicable):
Total conversion time =
tCNV x nAVG x nSCAN + tTS + tINT-REF,SU
where:
tCNV = tDOV (where tDOV is dependent from the clock
and reference mode selected)
nAVG = samples per result (amount of averaging)
nSCAN = number of times each channel is scanned; set
to one unless [SCAN1, SCAN0] = 10
tTS = time required for temperature measurement
(58.1µs); set to zero if temperature measurement is not
requested
tINT-REF,SU = tWU (external-reference wake-up); if a
conversion using the external reference is requested
In clock mode 01, the total conversion time depends on
how long CNVST is held low or high. Conversion time in
externally clocked mode (CKSEL1, CKSEL0 = 11)
depends on the SCLK period and how long CS is held
high between each set of eight SCLK cycles. In clock
mode 01, the total conversion time does not include the
time required to turn on the internal reference.
SCLK
DOUT
MSB1 LSB1 MSB2
(ACQUISITION1) (ACQUISITION2)
(CONVERSION1)
DIN (CONVERSION BYTE)
CS
EOC
X = DON'T CARE.
Figure 9. Clock Mode 11—Externally Timed Acquisition, Sampling, and Conversion without CNVST
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 33
tCSH
SCLK
DIN
DOUT
CS
1234 32
16
8
D15 D14 D13 D12 D11
5
D15
D7
D14
D6
D13
D5
D12
D4
D0
D1 D0
tDOD
tDOT
tCSS
tCSPWH
D1
tDOE
tDS
tDH
tCH
tCL
Figure 10. DAC/GPIO Serial-Interface Timing (Clock Modes 00, 01, and 10)
DAC/GPIO Timing
Figures 10–13 detail the timing diagrams for writing to
the DAC and GPIOs. Figure 10 shows the timing speci-
fications for clock modes 00, 01, and 10. Figure 11
shows the timing specifications for clock mode 11.
Figure 12 details the timing specifications for the DAC
input select register and 2 bytes to follow. Output data
is updated on the rising edge of SCLK in clock mode
11. Figure 13 shows the GPIO timing. Figure 14 shows
the timing details of a hardware LDAC command DAC-
register update. For a software-command DAC-register
update, tSis valid from the rising edge of CS, which fol-
lows the last data bit in the software command word.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
34 ______________________________________________________________________________________
SCLK
DIN
DOUT
1234
tCSPWH
tCSS
tDOE
tDS
tDH
tDOT
tCL
tCH
tCSH
tDOD
32
16
8
D15 D14 D13 D12 D11
5
D15
D7
D14
D6
D13
D5
D12
D4
D0
D1 D0
D1
CS
Figure 11. DAC/GPIO Serial-Interface Timing (Clock Mode 11)
SCLK
DIN
DOUT
CS
1289 24
BIT 7 (MSB) BIT 6 BIT 0 (LSB)
THE COMMAND BYTE
INITIALIZES THE DAC SELECT
REGISTER
THE NEXT 16 BITS SELECT THE DAC
AND THE DATA WRITTEN TO IT
BIT 15 BIT 14
10
BIT 0BIT 1
Figure 12. DAC-Select Register Byte and DAC Serial-Interface Word
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 35
GPIO INPUT/OUTPUT
CS
tGSU
tGOD
Figure 13. GPIO Timing
LDAC
tLDACPWL
tS
OUT_
±1 LSB
Figure 14. LDAC Functionality
LDAC Functionality
Drive LDAC low to transfer the content of the input reg-
isters to the DAC registers. Drive LDAC permanently
low to make the DAC register transparent. The DAC
output typically settles from zero to full scale within ±1
LSB after 2µs. See Figure 14.
Layout, Grounding, and Bypassing
For best performance, use PC boards. Ensure that digi-
tal and analog signal lines are separated from each
other. Do not run analog and digital signals parallel to
one another (especially clock signals) or do not run dig-
ital lines underneath the MAX1340/MAX1342/
MAX1346/MAX1348 package. High-frequency noise in
the AVDD power supply may affect performance.
Bypass the AVDD supply with a 0.1µF capacitor to
AGND, close to the AVDD pin. Bypass the DVDD supply
with a 0.1µF capacitor to DGND, close to the DVDD pin.
Minimize capacitor lead lengths for best supply-noise
rejection. If the power supply is very noisy, connect a
10Ωresistor in series with the supply to improve power-
supply filtering.
The MAX1340/MAX1342/MAX1346/MAX1348 thin QFN
packages contain an exposed pad on the underside of
the device. Connect this exposed pad to AGND. Refer to
the MAX1258EVKIT for an example of proper layout.
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line can be either a best-straight-line fit or a line
drawn between the end points of the transfer function,
once offset and gain errors have been nullified. INL for
the MAX1340/MAX1342/MAX1346/MAX1348 is mea-
sured using the end-point method.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A
DNL error specification of less than 1 LSB guarantees
no missing codes and a monotonic transfer function.
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
36 ______________________________________________________________________________________
Unipolar ADC Offset Error
For an ideal converter, the first transition occurs at 0.5
LSB, above zero. Offset error is the amount of deviation
between the measured first transition point and the
ideal first transition point.
Bipolar ADC Offset Error
While in bipolar mode, the ADC’s ideal midscale transi-
tion occurs at AGND -0.5 LSB. Bipolar offset error is the
measured deviation from this ideal value.
ADC Gain Error
Gain error is defined as the amount of deviation
between the ideal transfer function and the measured
transfer function, with the offset error removed and with
a full-scale analog input voltage applied to the ADC,
resulting in all ones at DOUT.
DAC Offset Error
DAC offset error is determined by loading a code of
all zeros into the DAC and measuring the analog
output voltage.
DAC Gain Error
DAC gain error is defined as the amount of deviation
between the ideal transfer function and the measured
transfer function, with the offset error removed, when
loading a code of all ones into the DAC.
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (tAD) is the time between the rising
edge of the sampling clock and the instant when an
actual sample is taken.
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital sam-
ples, signal-to-noise ratio (SNR) is the ratio of full-scale
analog input (RMS value) to the RMS quantization error
(residual error). The ideal, theoretical minimum analog-
to-digital noise is caused by quantization error only and
results directly from the ADC’s resolution (N bits):
SNR = (6.02 x N + 1.76)dB
In reality, there are other noise sources besides quanti-
zation noise, including thermal noise, reference noise,
clock jitter, etc. Therefore, SNR is calculated by taking
the ratio of the RMS signal to the RMS noise. RMS noise
includes all spectral components to the Nyquist fre-
quency excluding the fundamental, the first five har-
monics, and the DC offset.
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS equivalent of all other ADC output signals:
SINAD(dB) = 20 x log (SignalRMS / NoiseRMS)
Effective Number of Bits
Effective number of bits (ENOB) indicates the global
accuracy of an ADC at a specific input frequency and
sampling rate. An ideal ADC’s error consists of quanti-
zation noise only. With an input range equal to the full-
scale range of the ADC, calculate the ENOB as follows:
ENOB = (SINAD - 1.76) / 6.02
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first five harmonics of the input signal to the
fundamental itself. This is expressed as:
where V1is the fundamental amplitude, and V2through
V6are the amplitudes of the first five harmonics.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS value of the next largest distortion
component.
ADC Channel-to-Channel Crosstalk
Bias the ON channel to midscale. Apply a full-scale sine
wave test tone to all OFF channels. Perform an FFT on
the ON channel. ADC channel-to-channel crosstalk is
expressed in dB as the amplitude of the FFT spur at the
frequency associated with the OFF channel test tone.
Intermodulation Distortion (IMD)
IMD is the total power of the intermodulation products
relative to the total input power when two tones, f1 and
f2, are present at the inputs. The intermodulation prod-
ucts are (f1 ± f2), (2 x f1), (2 x f2), (2 x f1 ± f2), (2 x f2 ±
f1). The individual input tone levels are at -7dBFS.
Small-Signal Bandwidth
A small -20dBFS analog input signal is applied to an
ADC so the signal’s slew rate does not limit the ADC’s
performance. The input frequency is then swept up to
the point where the amplitude of the digitized conver-
sion result has decreased by -3dB. Note that the T/H
performance is usually the limiting factor for the small-
signal input bandwidth.
THD x VVVVVV= ++++
()
⎡
⎣
⎢⎤
⎦
⎥
20 22324252621
log /
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
______________________________________________________________________________________ 37
Full-Power Bandwidth
A large -0.5dBFS analog input signal is applied to an
ADC, and the input frequency is swept up to the point
where the amplitude of the digitized conversion result
has decreased by -3dB. This point is defined as full-
power input bandwidth frequency.
DAC Digital Feedthrough
DAC digital feedthrough is the amount of noise that
appears on the DAC output when the DAC digital con-
trol lines are toggled.
ADC Power-Supply Rejection
ADC power-supply rejection (PSR) is defined as the
shift in offset error when the power supply is moved
from the minimum operating voltage to the maximum
operating voltage.
DAC Power-Supply Rejection
DAC PSR is the amount of change in the converter’s
value at full-scale as the power-supply voltage changes
from its nominal value. PSR assumes the converter’s lin-
earity is unaffected by changes in the power-supply
voltage.
Chip Information
TRANSISTOR COUNT: 58,141
PROCESS: BiCMOS
Package Information
For the latest package outline information, go to
www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
36 TQFN T3666-3 21-0141
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
38 ______________________________________________________________________________________
Pin Configurations
D.C. 1
D.C. 2
3
DVDD 4
DGND 5
DOUT 6
SCLK 7
DIN 8
OUT0 9
EOC
AIN027
REF1
26
25
D.C.
24
N.C.
23
RES_SEL
22
21
20
D.C.
19
D.C.
OUT1
10
OUT2
11 12
AVDD
13
AGND
14
N.C.
15
D.C.
16
D.C.
17
D.C.
18
OUT3
36
REF2/AIN6
35 34
N.C.
33
N.C.
32
AIN4
31
AIN3
30
AIN2
29
AIN1
28
AIN5
LDAC
CS
CNVST/AIN7
MAX1340
TOP VIEW
6mm x 6mm x 0.8mm
THIN QFN
GPIOA0 1
GPIOA1 2
3
DVDD 4
DGND 5
DOUT 6
SCLK 7
DIN 8
OUT0 9
EOC
AIN027
REF1
26
25
GPIOC0
24
N.C.
23
RES_SEL
22
21
20
D.C.
19
GPIOC1
OUT1
10
OUT2
11 12
AVDD
13
AGND
14
N.C.
15
D.C.
16
D.C.
17
D.C.
18
OUT3
36
REF2/AIN6
35 34
N.C.
33
N.C.
32
AIN4
31
AIN3
30
AIN2
29
AIN1
28
AIN5
LDAC
CS
CNVST/AIN7
MAX1342
TOP VIEW
6mm x 6mm x 0.8mm
THIN QFN
D.C. 1
D.C. 2
3
DVDD 4
DGND 5
DOUT 6
SCLK 7
DIN 8
OUT0 9
EOC
AIN027
REF1
26
25
D.C.
24
N.C.
23
RES_SEL
22
21
20
D.C.
19
D.C.
OUT1
10
OUT2
11 12
AVDD
13
AGND
14
N.C.
15
D.C.
16
D.C.
17
D.C.
18
OUT3
36
REF2
35 34
N.C.
33
N.C.
32
D.C.
31
AIN3
30
AIN2
29
AIN1
28
D.C.
LDAC
CS
CNVST
MAX1346
TOP VIEW
6mm x 6mm x 0.8mm
THIN QFN
GPIOA0 1
GPIOA1 2
3
DVDD 4
DGND 5
DOUT 6
SCLK 7
DIN 8
OUT0 9
EOC
AIN027
REF1
26
25
GPIOC0
24
N.C.
23
RES_SEL
22
21
20
D.C.
19
GPIOC1
OUT1
10
OUT2
11 12
AVDD
13
AGND
14
N.C.
15
D.C.
16
D.C.
17
D.C.
18
OUT3
36
REF2
35 34
N.C.
33
N.C.
32
D.C.
31
AIN3
30
AIN2
29
AIN1
28
D.C.
LDAC
CS
CNVST
MAX1348
TOP VIEW
6mm x 6mm x 0.8mm
THIN QFN
MAX1340/MAX1342/MAX1346/MAX1348
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
39
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 3/08 Changed timing characteristic specification 7
