General Description
The MAX16832A/MAX16832C step-down constant-cur-
rent high-brightness LED (HB LED) drivers provide a
cost-effective design solution for automotive
interior/exterior lighting, architectural and ambient light-
ing, LED bulbs, and other LED illumination applications.
The MAX16832A/MAX16832C operate from a +6.5V to
+65V input voltage range and can provide an output
current up to 700mA, if operated up to a temperature of
+125°C, or up to a 1A if operated up to a temperature
of +105°C. A high-side current-sense resistor adjusts
the output current, and a dedicated pulse-width modu-
lation (PWM) input enables pulsed LED dimming over a
wide range of brightness levels.
These devices are well suited for applications requiring
a wide input voltage range. The high-side current sens-
ing and an integrated current-setting circuitry minimize
the number of external components while delivering an
average output current with ±3% accuracy. A hysteretic
control method ensures excellent input supply rejection
and fast response during load transients and PWM dim-
ming. The MAX16832A allows 10% current ripple, and
the MAX16832C allows 30% current ripple. Both
devices operate up to a 2MHz switching frequency,
thus allowing the use of small-sized components.
The MAX16832A/MAX16832C offer an analog dimming
feature that reduces the output current by applying an
external DC voltage below the internal 2V threshold volt-
age from TEMP_I to GND. TEMP_I also sources 25µA to
a negative temperature coefficient (NTC) thermistor con-
nected between TEMP_I and GND, thus providing an
analog thermal-foldback feature that reduces the LED
current when the temperature of the LED string exceeds
a specified temperature point. Additional features
include thermal-shutdown protection.
The MAX16832A/MAX16832C operate over the -40°C to
+125°C automotive temperature range and are available
in a thermally enhanced 8-pin SO package.
Applications
Architectural, Industrial, and Ambient Lighting
Automotive RCL, DRL, and Fog Lights
Heads-Up Displays
Indicator and Emergency Lighting
MR16 and MR111 LED Lights
Features
oHigh-Efficiency Solution
o6.5V to 65V Input Voltage Range
oOutput Current Up to 1A
oOn-Board 65V, 0.45ΩPower MOSFET
oHysteretic Control: Up to 2MHz Switching
Frequency
o±3% LED Current Accuracy
o200mV Current-Sense Reference
oResistor-Programmable Constant LED Current
oIntegrated High-Side Current Sense
oThermal-Foldback Protection/Linear Dimming
oThermal-Shutdown Protection
oAvailable in a Thermally Enhanced 8-Pin SO
Package
o-40°C to +125°C Operating Temperature Range
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
Ordering Information
LX
LXPGND
1
2
8
7
TEMP_I
DIMIN
GND
CS
3
4
6
5
MAX16832A
MAX16832C
L1
C2
ON
OFF
D1
HB LEDs
NTC*
*OPTIONAL
RSENSE
VIN
C1
Typical Application Circuit
19-4140; Rev 6; 7/12
1
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
+
Denotes a lead(Pb)-free/RoHS-compliant package.
*
EP = Exposed pad.
/V denotes an automotive qualified part.
PART TEMP RANGE
PIN-PACKAGE
MAX16832AASA+
-40°C to +125°C
8 SO-EP*
MAX16832AASA/V+
-40°C to +125°C
8 SO-EP*
MAX16832CASA+
-40°C to +125°C
8 SO-EP*
Pin Configuration appears at end of data sheet.
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
2
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = +24V, VDIM = VIN, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
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.
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
IN, CS, LX, DIM to GND .........................................-0.3V to +70V
TEMP_I to GND .......................................................-0.3V to +6V
PGND to GND ......................................................-0.3V to +0.3V
CS to IN .................................................................-0.3V to +0.3V
Maximum Current into Any Pin
(except IN, LX, and PGND).............................................20mA
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 18.9mW/°C above +70°C)...........1509.4mW
Operating Temperature Range
700mA (max) Output Current ........................-40°C to +125°C
1A (max) Output Current ...............................-40°C to +105°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Soldering (reflow).............................................................+260°C
Lead Temperature (soldering, 10s) .................................+300°C
Pin-to-Pin ESD Ratings......................................................±2.5kV
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage Range VIN 6.5 65 V
Ground Current No switching 1.5 mA
Supply Current VDIM < 0.6V, VIN = 12V 350 µA
UNDERVOLTAGE LOCKOUT (UVLO)
VCS = VIN - 100mV, VIN rising until VLX <
0.5VIN 6.25 6.5
Undervoltage Lockout UVLO VCS = VIN - 100mV, VIN falling until VLX >
0.5VIN 6.0
V
Undervoltage-Lockout Hysteresis 0.5 V
SENSE COMPARATOR
MAX16832A, VIN - VCS rising from 140mV
until VLX > 0.5VIN, VDIM = 5V 197 205 213
Sense Voltage Threshold High VSNSHI MAX16832C, VIN - VCS rising from 140mV
until VLX > 0.5VIN, VDIM = 5V 218 230 236
mV
MAX16832A, VIN - VCS falling from 260mV
until VLX < 0.5VIN , VDIM = 5V 185 190 198
Sense Voltage Threshold Low VSNSLO MAX16832C, VIN - VCS falling from 260mV
until VLX < 0.5VIN, VDIM = 5V 166 170 180
mV
Propagation Delay to Output High tDPDH Falling edge of VIN - VCS from 140mV to
260mV to VLX > 0.5VIN 50 ns
Propagation Delay to Output Low tDPDL Rising edge of VCS - VIN from 260mV to
140mV to VLX < 0.5VIN 50 ns
CS Input Current ICSIN VIN - VCS = 200mV, VIN = VCS 3.5 µA
PACKAGE THERMAL CHARACTERISTICS (Note 1)
SO-EP
Junction-to-Ambient Thermal Resistance (θJA)...............+53°C/W
Junction-to-Case Thermal Resistance (θJC)......................+5°C/W
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INTERNAL MOSFET
VIN = VDIM = 24V, VCS = 23.9V,
ILX = 700mA 0.45 0.9
Drain-to-Source Resistance RDSON VIN = VDIM = 6.0V, VCS = 5.9V,
ILX = 700mA 12
Ω
LX Leakage Current ILX_LEAK VDIM = 0V, VLX = 65V 10 µA
DIM INPUT
DIM Input-Voltage High VIH VIN - VCS = 100mV 2.8 V
DIM Input-Voltage Low VIL VCS - VIN = 100mV 0.6 V
DIM Turn-On Time tDIM_ON VDIM rising edge to VLX < 0.5VIN 60 ns
DIM Input Leakage High VDIM = VIN 815µA
DIM Input Leakage Low VDIM = 0V -3 -1.5 0 µA
THERMAL SHUTDOWN
Thermal-Shutdown Threshold Temperature rising +165 oC
Thermal-Shutdown Threshold
Hysteresis 10 oC
THERMAL FOLDBACK
Thermal-Foldback Enable
Threshold Voltage VTFB_ON VDIM = 5V 1.9 2.0 2.12 V
Thermal-Foldback Slope FBSLOPE VDIM = 5V 0.75 1/V
TEMP_I Output Bias Current ITEMP_I TA = +25 oC 25 26.5 28 µA
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +24V, VDIM = VIN, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
EFFICIENCY
vs. INPUT VOLTAGE
MAX16832A toc01
VIN (V)
EFFICIENCY (%)
5545352515
75
80
85
90
95
100
70
565
1 LED
3 LEDs
5 LEDs
7 LEDs9 LEDs 11 LEDs 13 LEDs 15 LEDs
9 LEDs
DUTY CYCLE
vs. INPUT VOLTAGE
MAX16832A toc02
VIN (V)
DUTY CYCLE (%)
5545352515
10
20
30
40
50
60
70
80
90
100
0
565
1 LED
3 LEDs
5 LEDs
7 LEDs
15 LEDs
13 LEDs
11 LEDs
FREQUENCY
vs. INPUT VOLTAGE
MAX16832A toc03
VIN (V)
FREQUENCY (kHz)
5545352515
50
100
150
200
250
300
350
400
450
500
0
565
1 LED
3 LEDs
5 LEDs
7 LEDs
9 LEDs
11 LEDs
13 LEDs 15 LEDs
16 LEDs
Typical Operating Characteristics
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA= +25°C, unless otherwise
noted.)
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
4
NORMALIZED ILED CURRENT
vs. INPUT VOLTAGE
MAX16832A toc04
VIN (V)
NORMALIZED ILED CURRENT
60555045403530252015105065
0.96
0.97
0.98
0.99
1.00
1.01
1.02
1.03
1.04
1.05
0.95
1 LED 3 LEDs 5 LEDs 7 LEDs 9 LEDs
11 LEDs
13 LEDs
15 LEDs
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX16832A toc05
VIN (V)
QUIESCENT CURRENT (µA)
605545 5015 20 25 30 35 40510
50
100
150
200
250
300
350
400
450
500
0
065
VDIM = 0V
PWM DIMMING
AT 200Hz (10% DUTY CYCLE)
MAX16832A toc06
1ms/div
ILED
200mA/div
0
0
VDIM
5V/div
VIN = 48V
8 LEDs
PWM DIMMING
AT 200Hz (90% DUTY CYCLE )
MAX16822A toc07
1ms/div
ILED
200mA/div
VDIM
5V/div
0
0
VIN = 48V
8 LEDs
PWM DIMMING
AT 20kHz (90% DUTY CYCLE)
MAX16832A toc08
10µs/div
ILED
200mA/div
VDIM
5V/div
0
0
VIN = 48V
8 LEDs
LED CURRENT
vs. VTEMP_I
MAX16832A toc09
VTEMP_I (V)
LED CURRENT (mA)
2.4
2.0
1.2 1.60.80.4
500
450
400
350
300
250
200
150
100
50
650
550
600
750
700
800
0
02.8
ILED
vs. TEMPERATURE
MAX16832A toc10
TEMPERATURE (°C)
ILED (A)
1109580655035205-10-25-40 125
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
VIN = 48V
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA= +25°C, unless otherwise
noted.)
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
5
LXRDSON
vs. TEMPERATURE
MAX16832A toc11
TEMPERATURE (°C)
LXRDSON (Ω)
1109580655035205-10-25
0.2
0.3
0.4
0.5
0.6
0.7
0.1
-40 125
VIN = 6.5V
VIN = 65V
VIN = 48V
ITEMP_I
vs. TEMPERATURE
MAX16832A toc12
ITEMP_I (µA)
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
29.5
30.0
25.0
TEMPERATURE (°C)
1109580655035205-10-25-40 125
VIN = 48V
Typical Operating Characteristics (continued)
(VIN = VDIM = 48V, RSENSE = 0.3Ω, L = 220µH (connected between IN and CS). Typical values are at TA= +25°C, unless otherwise
noted.)
Pin Description
PIN NAME FUNCTION
1 CS Current-Sense Input. Connect a resistor between IN and CS to program the LED current.
2 IN Positive Supply Voltage Input. Bypass with a 1µF or higher value capacitor to GND.
3 GND Ground
4 PGND Power Ground
5, 6 LX Switching Node
7 DIM Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to
enable the current regulator.
8 TEMP_I Thermal Foldback Control and Linear Dimming Input. Bypass with a 0.01µF capacitor to GND if
thermal foldback or analog dimming is used. See the Thermal Foldback section.
—EP
Exposed Pad. Connect EP to a large-area ground plane for effective power dissipation. Do not use
as the IC ground connection.
Detailed Description
The MAX16832A/MAX16832C are step-down, constant-
current, HB LED drivers. These devices operate from a
+6.5V to +65V input voltage range. The maximum output
is 1A, if the part is used at temperatures up to TA=
+105°C, or 700mA, if it is used up to TA= +125°C. A
high-side current-sense resistor sets the output current
and a dedicated PWM dimming input enables pulsed
LED dimming over a wide range of brightness levels.
A high-side current-sensing scheme and an on-board
current-setting circuitry minimize the number of exter-
nal components while delivering LED current with ±3%
accuracy, using a 1% sense resistor. See Figure 1 for a
functional diagram.
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
6
VCC
REGULATOR
OPEN LED
COMPARATOR LX
IN
CS
DIM
TEMP_I
VTFB_ON
2V
PGND
GND
CURRENT-SENSE
COMPARATOR
PWM
DIMMING
0.45Ω, 65V
nMOS SWITCH
UVLO
COMPARATOR
THERMAL
FOLDBACK
COMPARATOR
BANDGAP
REF
DIM
BUFFER
VCC _ANA
VCC _ANA
VCC _ANA
ISET
25µA
1.23V
GATE
DRIVER
MAX16832A
MAX16832C
Figure 1. Functional Diagram
Undervoltage Lockout (UVLO)
The MAX16832A/MAX16832C include a UVLO with
500mV hysteresis. The internal MOSFET turns off when
VIN falls below 5.5V to 6.0V.
DIM Input
LED dimming is achieved by applying a PWM signal at
DIM. A logic level below 0.6V at DIM forces the
MAX16832A/MAX16832Cs’ output low, thus turning off
the LED current. To turn the LED current on, the logic
level at DIM must be greater than 2.8V.
Thermal Shutdown
The MAX16832A/MAX16832C thermal-shutdown feature
turns off the LX driver when the junction temperature
exceeds +165°C. The LX driver turns back on when the
junction temperature drops 10°C below the shutdown
temperature threshold.
Analog Dimming
The MAX16832A/MAX16832C offer an analog-dimming
feature that reduces the output current when the volt-
age at TEMP_I is below the internal 2V threshold volt-
age. The MAX16832A/MAX16832C achieve analog
dimming by either an external DC voltage source con-
nected between TEMP_I and ground or by a voltage on
a resistor connected across TEMP_I and ground
induced by an internal current source of 25µA. When
the voltage at TEMP_I is below the internal 2V threshold
limit, the MAX16832A/MAX16832C reduce the LED cur-
rent. Use the following formula to set the analog dim-
ming current:
where VTFB_ON = 2V and FBSLOPE = 0.75 are obtained
from the
Electrical Characteristics
table and VAD is the
voltage at TEMP_I.
Thermal Foldback
The MAX16832A/MAX16832C include a thermal-fold-
back feature that reduces the output current when the
temperature of the LED string exceeds a specified tem-
perature point. These devices enter thermal-foldback
mode when the voltage drop on the NTC thermistor,
thermally attached to the LEDs and electrically con-
nected between TEMP_I and ground, drops below the
internal 2V threshold limit.
Applications Information
Selecting RSENSE to Set LED Current
The LED current is programmed with a current-sense
resistor connected between IN and CS. Use the follow-
ing equation to calculate the value of this resistor:
where VSNSHI is the sense voltage threshold high and
VSNSLO is the sense voltage threshold low (see the
Electrical Characteristics
table for values).
Current-Regulator Operation
The MAX16832A/MAX16832C regulate the LED current
using a comparator with hysteresis (see Figure 2). As
the current through the inductor ramps up and the volt-
age across the sense resistor reaches the upper
threshold, the internal MOSFET turns off. The internal
MOSFET turns on again when the inductor current
ramps down through the freewheeling diode until the
voltage across the sense resistor equals the lower
threshold. Use the following equation to determine the
operating frequency:
where n is the number of LEDs, VLED is the forward
voltage drop of 1 LED, and ∆V = (VSNSHI - VSNSLO).
Inductor Selection
The MAX16832A/MAX16832C operate up to a switch-
ing frequency of 2MHz. For space-sensitive applica-
tions, the high switching frequency allows the size of
the inductor to be reduced. Use the following formula to
calculate an approximate inductor value and use the
closest standard value:
For component selection, use the MAX16832A/C Design
Tool available at: www.maxim-ic.com/MAX16832-
software.
L approx VnV nV R
VVf
IN LED LED SENSE
IN SW
(.)
()
=××
××
−
∆
fVnV nV R
VVL
SW IN LED LED SENSE
IN
=××
××
−()
∆
RVVV
IA
SENSE SNSHI SNSLO
LED
() ()()
()
Ω= +1
2
IAI A FB VVVV
TF LED SLOPE TFB ON AD
() () ()
_
=× ⎛
⎝
⎜⎞
⎠
⎟×
()
⎡
⎣
⎢⎤
⎦
⎥
−−11
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
7
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
8
Freewheeling-Diode Selection
For stability and best efficiency, a low forward-voltage
drop diode with fast reverse-recovery time and low
capacitance is recommended. A Schottky diode is a
good choice as long as its breakdown voltage is high
enough to withstand the maximum operating voltage.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and stable operation. In normal operation, there
are two power loops. One is formed when the internal
MOSFET is on and the high current flows from ground
through the input cap, RSENSE, the LED load, the
inductor, and the internal MOSFET back to ground. The
second loop is formed when the internal MOSFET is off
and the high current circulates from the input cap posi-
tive terminal through RSENSE, the LED load, the induc-
tor, and the freewheeling diode and back to the input
cap positive terminal. Note that the current through
RSENSE, the LED load, and the inductor is basically DC
with some triangular ripple (low noise). The high-noise,
large signal, fast transition switching currents only flow
through the freewheeling diode to the input cap positive
terminal, or through the MOSFET to ground and then to
the input cap positive terminal. Without a proper PCB
layout, these square-wave switching currents can cre-
ate problems in a hysteretic LED driver.
The current control depends solely on the voltage
across RSENSE. Any noise pickup on this node induces
erratic switching of the internal MOSFET (the IC will
operate at a much higher frequency). To help prevent
this, place RSENSE as close as possible to CS and IN
and keep the sense traces short. It is especially impor-
tant to keep the square-wave switching currents in the
freewheeling diode away from RSENSE. To minimize
interference, place the freewheeling diode on the oppo-
site side of the IC as RSENSE and position the input
capacitor near the diode so it can return the high fre-
quency currents to ground. The layout in Figure 3
should be used as a guideline. The dashed line shows
the path of the high frequency components that cause
disruption in operation. For a good thermal design, the
exposed pad on the IC should solder to a large pad
with many vias to the backside ground plane.
fSW
t
tt2
∆I
t1
AVG. LED
CURRENT
HYSTERETIC
MODE
ILED
VDIM
Figure 2. Current-Regulator Operation
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
9
Chip Information
PROCESS: BiCMOS
LX
LXPGND
1
2
8
+
7
TEMP_I
DIMIN
GND
CS
SO-EP
TOP VIEW
3
4
6
5
MAX16832A
MAX16832C
Pin Configuration
D
1
VIAS FOR THERMAL TRANSFER
TO BACKSIDE GROUND PLANE
RSENSE
tOFF AND tON CURRENT PATHS
KEEP THIS LOOP TIGHT.
LED-
LED+
CFILTER
CIN
VIN
LX
GND
L
Figure 3. PCB Layout
PACKAGE
TYPE
PACKAGE
CODE OUTLINE NO. LAND
PATTERN NO.
8 SO-EP S8E-12 21-0111 90-0150
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package draw-
ings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
MAX16832A/MAX16832C
2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
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. 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.
10
_______________Maxim Integrated Products, Inc. 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 5/08 Initial release —
1 9/08 Introduced the MAX16832C 1
2 5/09 Revised General Description, Features, Absolute Maximum Ratings, and
Detailed Description 1, 2, 5
3 2/10 Updated PCB Layout Guidelines and added Figure 3 8, 9
4 8/10 Corrected Functional Diagram and added Soldering (reflow) to Absolute
Maximum Ratings 2, 5, 6
5 3/12 Updated Sense Voltage Threshold High and DIM Turn-On Time in Electrical
Characteristics 2, 3
6 7/12 Added automotive qualified part to Ordering Information 1
