General Description
The MAX9814 is a low-cost, high-quality microphone
amplifier with automatic gain control (AGC) and
low-noise microphone bias. The device features a
low-noise preamplifier, variable gain amplifier (VGA), output
amplifier, microphone-bias-voltage generator, and AGC
control circuitry.
The low-noise preamplifier has a fixed 12dB gain, while
the VGA gain automatically adjusts from 20dB to 0dB,
depending on the output voltage and the AGC threshold.
The output amplifier offers selectable gains of 8dB, 18dB,
and 28dB. With no compression, the cascade of the
amplifiers results in an overall gain of 40dB, 50dB, or 60dB.
A trilevel digital input programs the output amplifier gain. An
external resistive divider controls the AGC threshold and
a single capacitor programs the attack/release times. A
trilevel digital input programs the ratio of attack-to-release
time. The hold time of the AGC is fixed at 30ms. The low-
noise microphone-bias-voltage generator can bias most
electret microphones.
The MAX9814 is available in the space-saving, 14-pin
TDFN package. This device is specified over the -40°C to
+85°C extended temperature range.
Applications
●Digital Still Cameras
●Digital Video Cameras
●PDAs
●Bluetooth Headsets
●Entertainment Systems (e.g., Karaoke)
●Two-Way Communicators
●High-Quality Portable Recorders
●IP Phones/Telephone Conferencing
Features
●Automatic Gain Control (AGC)
●Three Gain Settings (40dB, 50dB, 60dB)
●Programmable Attack Time
●Programmable Attack and Release Ratio
●2.7V to 5.5V Supply Voltage Range
● Low Input-Referred Noise Density of 30nV/√Hz
●Low THD: 0.04% (typ)
●Low-Power Shutdown Mode
●Internal Low-Noise Microphone Bias, 2V
●Available in the Space-Saving, 14-Pin TDFN
(3mm x 3mm) Package
●-40°C to +85°C Extended Temperature Range
19-0764; Rev 3; 8/16
Ordering Information appears at end of data sheet.
LOW-NOISE
REFERENCE AGC
2.7V TO 5.5V
LNA
+12dB
VGA
+20dB/0dB
GAIN
+8/+18/
+28dB
MICBIAS
RMICBIAS
MICIN MICOUT
COUT
GND
CIN
VDD
SHDN
MAX9814
MAX9814 Microphone Amplifier with AGC and
Low-Noise Microphone Bias
Simplied Block Diagram
EVALUATION KIT AVAILABLE
VDD to GND ............................................................-0.3V to +6V
All Other Pins to GND .............................. -0.3V to (VDD + 0.3V)
Output Short-Circuit Duration .................................... Continuous
Continuous Current (MICOUT, MICBIAS) ......................±100mA
All Other Pins ...................................................................±20mA
Continuous Power Dissipation (TA = +70°C)
14-Pin TDFN-EP
(derate 16.7mW/°C above +70°C) ........................1481.5mW
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ...................................................... +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Bump Temperature (soldering) Reflow ............................ +235°C
(VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2μF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values
are at TA = +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
GENERAL
Operating Voltage VDD Guaranteed by PSRR test 2.7 5.5 V
Supply Current IDD 3.1 6 mA
Shutdown Supply Current ISHDN 0.01 1 µA
Input-Referred Noise Density enBW = 20kHz, all gain settings 30 nV/√Hz
Output Noise BW = 20kHz 430 µVRMS
Signal-to-Noise Ratio SNR
BW = 22Hz to 22kHz
(500mVRMS output signal) 61 dB
A-weighted 64
Dynamic Range DR (Note 2) 60 dB
Total Harmonic Distortion Plus
Noise THD+N
fIN = 1kHz, BW = 20Hz to 20kHz,
RL = 10kΩ, VTH = 1V (threshold = 2VP-P),
VIN = 0.5mVRMS, VCT = 0V
0.04
%
fIN = 1kHz, BW = 20Hz to 20kHz,
RL = 10kΩ, VTH = 0.1V (threshold =
200mVP-P), VIN = 30mVRMS, VCT = 2V
0.2
Amplier Input BIAS VIN 1.14 1.23 1.32 V
Maximum Input Voltage VIN_MAX 1% THD 100 mVP-P
Input Impedance ZIN 100 kΩ
Maximum Gain A
GAIN = VDD 39.5 40 40.5
dBGAIN = GND 49.5 50 50.6
GAIN = unconnected 59.5 60 60.5
Minimum Gain
GAIN = VDD 18.7 20 20.5
dBGAIN = GND 29.0 30 30.8
GAIN = unconnected 38.7 40 40.5
Maximum Output Level VOUT_RMS 1% THD+N, VTH = MICBIAS 0.707 VRMS
Regulated Output Level AGC enabled, VTH = 0.7V 1.26 1.40 1.54 VP-P
AGC Attack Time tATTACK CCT = 470nF (Note 3) 1.1 ms
Attack/Release Ratio A/R
A/R = GND 1:500
ms/msA/R = VDD 1:2000
A/R = unconnected 1:4000
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
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Absolute Maximum Ratings
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.
Electrical Characteristics
(VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2μF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values
are at TA = +25°C.) (Note 1)
Note 1: Devices are production tested at TA = +25°C. Limits over temperature are guaranteed by design.
Note 2: Dynamic range is calculated using the EIAJ method. The input is applied at -60dBFS (0.707μVRMS), fIN = 1kHz.
Note 3: Attack time measured as time from AGC trigger to gain reaching 90% of its final value.
Note 4: CG is connected to an external DC voltage source, and adjusted until VMICOUT = 1.23V.
Note 5: CG connected to GND with 2.2μF.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MICOUT High Output Voltage VOH IOUT sourcing 1mA 2.45 V
MICOUT Low Output Voltage VOL IOUT sinking 1mA 3 mV
MICOUT Bias MICOUT unconnected 1.14 1.23 1.32 V
Output Impedance ZOUT 50 Ω
Minimum Resistive Load RLOAD_MIN 5kΩ
Maximum Capacitive Drive CLOAD_MAX 200 pF
Maximum Output Current I
OUT_MAX 1% THD, RL = 500Ω 1 2 mA
Output Short-Circuit Current ISC 3 8 mA
Power-Supply Rejection Ratio PSRR
AGC mode; VDD = 2.7V to 5.5V (Note 4) 35 50
dB
f = 217Hz, VRIPPLE = 100mVP-P (Note 5) 55
f = 1kHz, VRIPPLE = 100mVP-P (Note 5) 52.5
f = 10kHz, VRIPPLE = 100mVP-P (Note 5) 43
MICROPHONE BIAS
Microphone Bias Voltage VMICBIAS IMICBIAS = 0.5mA 1.84 2.0 2.18 V
Output Resistance RMICBIAS IMICBIAS = 1mA 1 Ω
Output Noise Voltage VMICBIAS_NOISE IMICBIAS = 0.5mA, BW = 22Hz to 22kHz 5.5 µVRMS
Power-Supply Rejection Ratio PSRR
DC, VDD = 2.7V to 5.5V 70 80
dB
IMICBIAS = 0.5mA, VRIPPLE = 100mVP-P,
fIN = 1kHz 71
TRILEVEL INPUTS (A/R, GAIN)
Trilevel Input Leakage Current
A/R or GAIN = VDD
0.5VDD
/ 180kΩ
0.5VDD
/ 100kΩ
0.5VDD
/ 50kΩ mA
A/R or GAIN = GND 0.5VDD
/ 180kΩ
0.5VDD
/ 100kΩ
0.5VDD
/ 50kΩ
Input High Voltage VIH VDD x 0.7 V
Input Low Voltage VIL VDD x 0.3 V
Shutdown Enable Time tON 60 ms
Shutdown Disable Time tOFF 40 ms
DIGITAL INPUT (SHDN)
SHDN Input Leakage Current -1 +1 µA
Input High Voltage VIH 1.3 V
Input Low Voltage VIL 0.5 V
AGC THRESHOLD INPUT (TH)
TH Input Leakage Current -1 +1 µA
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
www.maximintegrated.com Maxim Integrated
│
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Electrical Characteristics (continued)
(VDD = 5V, CCT = 470nF, CCG = 2.2μF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1μF,
TA = +25°C, unless otherwise noted.)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9814 toc02
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-70
-60
-50
-40
-30
-20
-10
0
-80
10 100k
VRIPPLE = 200mVP-P
MICBIAS POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9814 toc03
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-100
-90
-80
-70
-60
-50
-40
-30
-110
10 100k
VRIPPLE = 200mVP-P
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9814 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.55.04.0 4.53.53.0
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
2.5
2.5 6.0
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
MAX9814 toc05
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (nA)
5.55.04.54.03.53.0
0.1
0.2
0.3
0.4
0.5
0
2.5 6.0
MICROPHONE BIAS VOLTAGE
vs. MICROPHONE BIAS SOURCE CURRENT
MAX9814 toc06
IMICBIAS (mA)
VMICBIAS VOLTAGE (V)
252015105
0.5
1.0
1.5
2.0
2.5
0
0 30
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9814 toc07
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.1
1
10
0.01
10 100k
VOUT = 800mVRMS
GAIN vs. FREQUENCY
MAX9814 toc01
FREQUENCY (Hz)
GAIN (dB)
10k1k100
10
20
30
40
50
60
70
80
0
10 100k
GAIN = UNCONNECTED
GAIN = 0
GAIN = 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT VOLTAGE
MAX9814 toc08
OUTPUT VOLTAGE (VRMS)
THD+N (%)
1.0
0.5
0.1
1
10
0.01
0 1.5
fIN = 300Hz, 1kHz,
and 3kHz
fIN = 10kHz
INPUT-REFERRED NOISE
vs. FREQUENCY
MAX9814 toc09
FREQUENCY (kHz)
INPUT-REFERRED NOISE (µVRMS/Hz)
1010.1
100
10
0.01 100
1000
1
MICIN AC-COUPLED
TO GND
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
Maxim Integrated
│
4
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Typical Operating Characteristics
(VDD = 5V, CCT = 470nF, CCG = 2.2μF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1μF,
TA = +25°C, unless otherwise noted.)
MICBIAS NOISE vs. FREQUENCY
MAX9814 toc10
FREQUENCY (Hz)
MICBIAS NOISE (nV
RMS
/Hz)
10k1k100
100
1000
10,000
10
10 100k
SMALL-SIGNAL PULSE RESPONSE
MAX9814 toc11
200µs/div
VMICIN
10mV/div
0V
VMICOUT
500mV/div
0V
CL = 10pF
TURN-ON RESPONSE
MAX9814 toc12
20µs/div
VSHDN
5V/div
0V
VMICBIAS
2V/div
0V
VMICOUT
1V/div
0V
VOUT vs. VIN
MAX9814 toc13
VIN (mVRMS)
V
OUT
(V
RMS
)
10050
0.25
0.50
0.75
1.00
0
0 150
VTH = 1V
VTH = 0.75V
VTH = 0.5V AGC ENABLED
GAIN = 1
VOUT vs. VIN
MAX9814 toc14
VIN (mVRMS)
VOUT (VRMS)
302010
0.25
0.50
0.75
1.00
0
0 40
VTH = 1V
VTH = 0.75V
VTH = 0.5V
AGC ENABLED
GAIN = 0
VOUT vs. VIN
MAX9814 toc15
VIN (mVRMS)
VOUT (VRMS)
105
0.25
0.50
0.75
1.00
0
0 15
VTH = 1V
VTH = 0.75V
VTH = 0.5V
AGC ENABLED
GAIN = UNCONNECTED
ATTACK TIME
MAX9814 toc16
200µs/div
VMICOUT
500mV/div
CCT = 47nF
0V
ATTACK TIME
MAX9814 toc17
200µs/div
VMICOUT
500mV/div
CCT = 100nF
0V
HOLD AND RELEASE TIME
MAX9814 toc18
20ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = GND
0V
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
Maxim Integrated
│
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Typical Operating Characteristics (continued)
(VDD = 5V, CCT = 470nF, CCG = 2.2μF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1μF,
TA = +25°C, unless otherwise noted.)
HOLD AND RELEASE TIME
MAX9814 toc19
40ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = VDD
0V
HOLD AND RELEASE TIME
MAX9814 toc20
100ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = UNCONNECTED
0V
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
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Typical Operating Characteristics (continued)
PIN NAME FUNCTION
TDFN
1 CT Timing Capacitor Connection. Connect a capacitor to CT to control the Attack and Release times of
the AGC.
2SHDN Active-Low Shutdown Control
3 CG Amplier DC Offset Adjust. Connect a 2.2µF capacitor to GND to ensure zero offset at the output.
4, 11 N.C. No Connection. Connect to GND.
5 VDD Power Supply. Bypass to GND with a 1µF capacitor.
6 MICOUT Amplier Output
7 GND Ground
8 MICIN Microphone Noninverting Input
9 A/R
Trilevel Attack and Release Ratio Select. Controls the ratio of attack time to release time for the
AGC circuit.
A/R = GND: Attack/Release Ratio is 1:500
A/R = VDD: Attack/Release Ratio is 1:2000
A/R = Unconnected: Attack/Release Ratio is 1:4000
10 GAIN
Trilevel Amplier Gain Control.
GAIN = VDD, gain set to 40dB.
GAIN = GND, gain set to 50dB.
GAIN = Unconnected, uncompressed gain set to 60dB.
12 BIAS Amplier Bias. Bypass to GND with a 0.47µF capacitor.
13 MICBIAS Microphone Bias Output
14 TH AGC Threshold Control. TH voltage sets gain control threshold. Connect TH to MICBIAS to disable
the AGC.
— EP Exposed Pad. Connect the TDFN EP to GND.
MAX9814
TDFN
TOP VIEW
2 4 5
13 11 10
MICBIAS
N.C.
GAIN
SHDN
N.C.
VDD
1
14
+
THCT
3
12
BIASCG
6
9
A/RMICOUT
7
8
MICINGND
*EP
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
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Pin Description
Pin Conguration
Detailed Description
The MAX9814 is a low-cost, high-quality microphone
amplifier with automatic gain control (AGC) and a low-
noise microphone bias. The MAX9814 consists of several
distinct circuits: a low-noise preamplifier, a variable gain
amplifier (VGA), an output amplifier, a microphone-bias-
voltage generator, and AGC control circuitry.
An internal microphone bias voltage generator provides
a 2V bias that is suitable for most electret condenser
microphones. The MAX9814 amplifies the input in three
distinct stages. In the first stage, the input is buffered and
amplified through the low-noise preamplifier with a gain of
12dB. The second stage consists of the VGA controlled
by the AGC. The VGA/AGC combination is capable of
varying the gain from 20dB to 0dB. The output amplifier is
the final stage in which a fixed gain of 8dB, 18dB, 20dB is
programmed through a single trilevel logic input. With no
compression from the AGC, the MAX9814 is capable of
providing 40dB, 50dB, or 60dB gain.
Automatic Gain Control (AGC)
A device without AGC experiences clipping at the output
when too much gain is applied to the input. AGC prevents
clipping at the output when too much gain is applied to
the input, eliminating output clipping. Figure 1 shows a
comparison of an over-gained microphone input with and
without AGC.
The MAX9814’s AGC controls the gain by first detecting
that the output voltage has exceeded a preset limit. The
microphone amplifier gain is then reduced with a select-
able time constant to correct for the excessive output-
voltage amplitude. This process is known as the attack
time. When the output signal subsequently lowers in
amplitude, the gain is held at the reduced state for a short
period before slowly increasing to the normal value. This
process is known as the hold and release time. The speed
at which the amplifiers adjust to changing input signals is
set by the external timing capacitor CCT and the voltage
applied to A/R. The AGC threshold can be set by adjusting
VTH. Gain reduction is a function of input signal ampli-
tude with a maximum AGC attenuation of 20dB. Figure 2
shows the effect of an input burst exceeding the preset
limit, output attack, hold and release times.
If the attack-and-release times are configured to respond
too fast, audible artifacts often described as “pumping”
or “breathing” can occur as the gain is rapidly adjusted
to follow the dynamics of the signal. For best results,
adjust the time constant of the AGC to accommodate
the source material. For applications in which music CDs
are the main audio source, a 160μs attack time with an
80ms release time is recommended. Music applications
typically require a shorter release time than voice or
movie content.
Figure 1. Microphone Input with and Without AGC
MAX9814 AGC DISABLED
400µs/div
VMICIN
100mV/div
VMICOUT
(AC-COUPLED)
1V/div
MAX9814 fig01a
MAX9814 AGC ENABLED
400µs/div
VMICIN
100mV/div
VMICOUT
(AC-COUPLED)
1V/div
MAX9814 fig01b
0V
0V
0V
0V
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
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│
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Attack Time
The attack time is the time it takes for the AGC to reduce
the gain after the input signal has exceeded the thresh-
old level. The gain attenuation during the attack time is
exponential, and defined as one-time constant. The time
constant of the attack is given by 2400 x CCT seconds
(where CCT is the external timing capacitor):
● Use a short attack time for the AGC to react quickly to
transient signals, such as snare drum beats (music) or
gun shots (DVD).
● Use a longer attack time to allow the AGC to ignore
short-duration peaks and only reduce the gain when a
noticeable increase in loudness occurs. Short-duration
peaks are not reduced, but louder passages are. This
allows the louder passages to be reduced in volume,
thereby maximizing output dynamic range.
Hold Time
Hold time is the delay after the signal falls below the
threshold level before the release phase is initiated. Hold
time is internally set to 30ms and nonadjustable. The hold
time is cancelled by any signal exceeding the set thresh-
old level, and the attack time is reinitiated.
Release Time
The release time is how long it takes for the gain to return
to its normal level after the output signal has fallen below
the threshold level and 30ms hold time has expired.
Release time is defined as release from a 20dB gain com-
pression to 10% of the nominal gain setting after the input
signal has fallen below the TH threshold and the 30ms
hold time has expired. Release time is adjustable and has
a minimum of 25ms. The release time is set by picking an
attack time using CCT and setting the attack-to-release
time ratio by configuring A/R, as shown in Table 1:
● Use a small ratio to maximize the speed of the AGC.
● Use a large ratio to maximize the sound quality and
prevent repeated excursions above the threshold from
being independently adjusted by the AGC.
AGC Output Threshold
The output threshold that activates AGC is adjustable
through the use of an external resistive divider. Once the
divider is set, AGC reduces the gain to match the output
voltage to the voltage set at the TH input.
Microphone Bias
The MAX9814 features an internal low-noise microphone
bias voltage capable of driving most electret condenser
microphones. The microphone bias is regulated at 2V to
provide that the input signal to the low-noise preamplifier
does not clip to ground.
Applications Information
Programming Attack-and-Release Times
Attack-and-release times are set by selecting the
capacitance value between CT and GND, and by setting
the logic state of A/R (Table 1). A/R is a trilevel logic input
that sets the attack-to-release time ratio.
The attack-and-release times can be selected by utilizing
the corresponding capacitances listed in Table 2.
Figure 2. Input Burst Exceeding AGC Limit
Table 1. Attack-and-Release Ratios
Table 2. Attack-and-Release Time
A/R ATTACK/RELEASE RATIO
GND 1:500
VDD 1:2000
Unconnected 1:4000
CCT
tATTACK
(ms)
tRELEASE (ms)
A/R =
GND
A/R =
VDD
A/R =
UNCONNECTED
22nF 0.05 25 100 200
47nF 0.11 55 220 440
68nF 0.16 80 320 640
100nF 0.24 120 480 960
220nF 0.53 265 1060 2120
470nF 1.1 550 2200 4400
680nF 1.63 815 3260 6520
1µF 2.4 1200 4800 9600
10ms/div
VCT
500mV/div
VMICOUT
(AC-COUPLED)
1V/div
ATTACK RELEASE
HOLD
0V
0V
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
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Setting the AGC Threshold
To set the output-voltage threshold at which the
microphone output is clamped, an external resistor-divider
must be connected from MICBIAS to ground with the out-
put of the resistor-divider applied to TH. The voltage VTH
determines the peak output-voltage threshold at which the
output becomes clamped. The maximum signal swing at
the output is then limited to two times VTH and remains at
that level until the amplitude of the input signal is reduced.
To disable AGC, connect TH to MICBIAS.
Microphone Bias Resistor
MICBIAS is capable of sourcing 20mA. Select a value for
RMICBIAS that provides the desired bias current for the
electret microphone. A value of 2.2kΩ is usually sufficient
for a microphone of typical sensitivity. Consult the micro-
phone data sheet for the recommended bias resistor.
Bias Capacitor
The BIAS output of the MAX9814 is internally buffered
and provides a low-noise bias. Bypass BIAS with a 470nF
capacitor to ground.
Input Capacitor
The input AC-coupling capacitor (CIN) and the input
resistance (RIN) to the microphone amplifier form a high-
pass filter that removes any DC bias from an input signal
(see the Typical Application Circuit/Functional Diagram).
CIN prevents any DC components from the input-signal
source from appearing at the amplifier outputs. The -3dB
point of the highpass filter, assuming zero source imped-
ance due to the input signal source, is given by:
3dB_IN IN IN
1
f2R C
−=
π× ×
Choose CIN such that f-3dB_IN is well below the lowest
frequency of interest. Setting f-3dB_IN too high affects the
amplifier’s low-frequency response. Use capacitors with
low-voltage coefficient dielectrics. Aluminum electrolytic,
tantalum, or film dielectric capacitors are good choices
for AC-coupling capacitors. Capacitors with high-voltage
coefficients, such as ceramics (non-C0G dielectrics), can
result in increased distortion at low frequencies.
Output Capacitor
The output of the MAX9814 is biased at 1.23V. To
eliminate the DC offset, an AC-coupling capacitor (COUT)
must be used. Depending on the input resistance (RL) of
the following stage, COUT and RL effectively form a high-
pass filter. The -3dB point of the highpass filter, assuming
zero output impedance, is given by:
3dB_OUT L OUT
1
f2R C
−=
π× ×
Shutdown
The MAX9814 features a low-power shutdown mode.
When SHDN goes low, the supply current drops to
0.01μA, the output enters a high-impedance state, and
the bias current to the microphone is switched off. Driving
SHDN high enables the amplifier. Do not leave SHDN
unconnected.
Power-Supply Bypassing and PCB Layout
Bypass the power supply with a 0.1μF capacitor to
ground. Reduce stray capacitance by minimizing trace
lengths and place external components as close to
the device as possible. Surface-mount components are
recommended. In systems where analog and digital
grounds are available, connect the MAX9814 to analog
ground.
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
www.maximintegrated.com Maxim Integrated
│
10
AGC
MICBIAS
BIAS
RMICBIAS
2.21kΩ
R1
150kΩ
R2
100kΩ
MICIN COUT
GND
VDD
CIN
0.1µF
A/R
MICBIAS
GAIN
TH
MICOUT
VDD
VDD
SHDN
CBYPASS
1µF
CBIAS
0.47µF
CG
CCG
2.2µF
CT
CCT
470nF
REF
LNA VGA
ROUT
*THE DEVICE HAS BEEN CONFIGURED WITH AN ATTACK TIME OF 1.1µs, 40dB GAIN, AND AN ATTACK-AND-RELEASE RATIO OF 1:500.
MAX9814
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
www.maximintegrated.com Maxim Integrated
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11
Typical Application Circuit/Functional Diagram
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
/V denotes an automotive qualified part.
**Future product—contact factory for availability.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
14 TDFN-EP T1433+2 21-0137 90-0062
PART TEMP RANGE PIN-PACKAGE
MAX9814ETD+T -40°C to +85°C 14 TDFN-EP*
MAX9814ETD/V+T** -40°C to +85°C 14 TDFN-EP*
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
www.maximintegrated.com Maxim Integrated
│
12
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character,
but the drawing pertains to the package regardless of RoHS
status.
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 3/07 Initial release —
1 2/09 Updated Ordering Information, Absolute Maximum Ratings, Pin Description, and Pin
Conguration sections to include EP for TDFN package 1, 2, 6, 11
2 6/09 Removed UCSP package 1, 2, 6, 11, 12
3 8/16 Updated and moved Ordering Information and Package Information tables 1, 12
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX9814 Microphone Amplier with AGC and
Low-Noise Microphone Bias
© 2016 Maxim Integrated Products, Inc.
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13
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
