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MAX16831ATJ+-MAX16831ATJ+T
High-Voltage, High-Power LED Driver with Analog and PWM Dimming Control
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming ControlEVALUATION KIT AVAILABLE
General DescriptionThe MAX16831 is a current-mode, high-brightness LED
(HBLED) driver designed to control two external
n-channel MOSFETs for the single-string LED current
regulation. The MAX16831 integrates all the building
blocks necessary to implement fixed-frequency HBLED
drivers with wide-range dimming control. The
MAX16831 is configurable to operate as a step-down
(buck), step-up (boost), or step-up/-down (buck-boost)
current regulator.
Current-mode control with leading-edge blanking simpli-
fies control-loop design. Internal slope compensation
stabilizes the current loop when operating at duty cycles
above 50%. The MAX16831 operates over a wide input
voltage range and is capable of withstandingautomo-
tive load-dump events. Multiple MAX16831s can be
synchronized to each other or to an external clock. The
MAX16831 includes a floating dimming driver for
brightness control with an external n-channel MOSFET
in series with the LED string.
HBLED drivers using the MAX16831 achieve efficien-
cies of over 90% in automotive applications. The
MAX16831 also includes a 1.4A source and 2.5A sink
gate driver for driving switching MOSFETs in high-power
LED driver applications, such as front light assemblies.
The dimming control allows for wide PWM dimming at
frequencies up to 2kHz. Higher dimming ratios of up to
1000:1 are achievable at lower dimming frequencies.
The MAX16831 is available in a 32-pin thin QFN package
with exposed pad and operates over the -40°C to
+125°C automotive temperature range.
ApplicationsAutomotive Exterior Lighting:
High-Beam/Low-Beam/Signal Lights
Rear Combination Lights (RCL)
Daytime Running Lights (DRL)
Fog Light and Adaptive Front Light Assemblies
Industrial and Architectural Lighting
Emergency Lighting
Projectors with RGB LED Light Sources
Navigation and Marine Indicators
FeaturesWide Input Range: 6V to 76V With Cold-Start
Operation to 5.5VIntegrated Differential LED Current-Sense
AmplifierFloating Dimming Driver Capable of Driving an
n-Channel MOSFET5% LED Current Accuracy200Hz On-Board Ramp Syncs to External PWM
Dimming SignalProgrammable Switching Frequency (125kHz to
600kHz) and SynchronizationOutput Overvoltage Load Dump, LED Short,
Overtemperature ProtectionLow 107mV LED Current Sense for High
EfficiencyEnable/Shutdown Input with Shutdown Current
Below 45µA
Ordering Information
PARTTEMP RANGEPIN-PACKAGEMAX16831ATJ+-40°C to +125°C32 TQFN-EP*
MAX16831ATJ/V+-40°C to +125°C32 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
/V denotes an automotive qualified part.
VIN
DIM
RCSRT
CREG1
RUV2
DRV
DRI
REG1
DIM
VCC
SNS+
QGND
RTSYNC
CS-CS+LO
COMPREG2
DGT
UVEN
SNS-
AGND
RSENSE
ROV1
ROV2
CLMP
SGND
CCLMP
CREG2R1
LEDs
BUCK-BOOST CONFIGURATIONRUV1
CUVEN
MAX16831
Typical Operating Circuits
Pin Configuration appears at end of data sheet.
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 1µF, CCLMP= 0.1µF, RT= 25kΩ, TA= TJ = -40°C to +125°C, unless otherwise noted.
Typical specifications 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.
VCC, HI, LO, CLMP to QGND.................................-0.3V to +80V
CS+, CS-, DGT, UVEN to QGND............................-0.3V to +80V
UVEN to QGND..........................................-0.3V to (VCC+ 0.3V)
DRV to SGND.........................................................-0.3V to +18V
DRI, REG2, DIM to AGND......................................-0.3V to +18V
QGND, SGND to AGND........................................-0.3V to +0.3V
SNS+ to SNS-...........................................................-0.3V to +6V
CS, FB, COMP, SNS+, SNS-, OV, REF,
RTSYNC to AGND.................................................-0.3V to +6V
REG1, CLKOUT to AGND........................................-0.3V to +6V
CS+ to CS-.............................................................-0.3V to +12V
HI to LO..................................................................-0.3V to +36V
CS+, CS-, DGT, CLMP to LO.................................-0.3V to +12V
CS+, CS-, DGT, CLMP to LO........................-0.3V to (HI + 0.3V)
HI to CLMP.............................................................-0.3V to +28V
Continuous Power Dissipation* (TA= +70°C)
32-Pin TQFN (derate 34.5mW/°C above +70°C)........2758mW
Thermal Resistance*θJA.................................................................................29°C/WθJC................................................................................1.7°C/W
Operating Temperature Range.........................-40°C to +125°C
Maximum Junction Temperature.....................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Reflow Temperature.........................................................+240°C
Lead Temperature (soldering, 10s).................................+300°C
*As per JEDEC 51 standard, multilayer board (PCB).
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput Voltage RangeVCC5.576.0V
Supply CurrentIQIREG2 = 0A2.74.5mA
Shutdown CurrentISHDNVUVEN ≤ 0.8V2545µA
UVENVCC_RVCC rising5.56.0VCC UVLO ThresholdVCC_FVCC falling5.05.5V
VCC Threshold HysteresisVCC_HYS0.4V
VUVRVUVEN rising1.1001.2441.360UVEN ThresholdVUVFVUVEN falling1.0001.1451.260V
UVEN Input CurrentIUVENVUVEN = 0V and VUVEN = 76V, VCC = 77V-0.2+0.2µA
REGULATORS0 ≤ IREG1 ≤ 2mA, 7.5V ≤ VCC ≤ 76V4.755.005.25REG1 Regulator OutputVREG1IREG1 = 2mA, VCC = 5.7V4.004.505.25V
REG1 Dropout VoltageIREG1 = 2mA (Note 1)0.51.0V
REG1 Load Regulation∆V/∆IVCC = 7.5V, 0 ≤ IREG1 ≤ 2mA25Ω
7.5V ≤ VCC ≤ 76V, IREG2 = 1mA6.657.007.35REG2 Regulator OutputVREG2VCC = 5.7V, 0 ≤ IREG2 ≤ 20mA4.55.0V
REG2 Dropout VoltageIREG2 = 20mA (Note 1)0.5V
REG2 Load Regulation∆V/∆IVCC = 7.5V, 0 ≤ IREG2 ≤ 20mA25Ω
HIGH-SIDE REGULATOR (CLMP) (All Voltages Referred to LO) (Note 2)CLMP UVLO ThresholdVCLMPTHVCLMP rising2.02.53.0V
CLMP UVLO Threshold
HysteresisVCLMPHYS0.22V
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS8.7V ≤ (VHI - VLO) ≤ 36V, ICLMP = 1mA5.58.010.0
CLMP Regulator Output VoltageVCLMP5.0V ≤ (VHI - VLO) ≤ 8.7V, ICLMP = 250µA(VHI - VLO)
- 0.7
CURRENT-SENSE AMPLIFIER (CSA)Differential Input Voltage RangeVCS+ -
VCS-00.3V
Common-Mode Range0VCCV
CS+ Input Bias CurrentICS+VCS+ - VCS- = 0.3V-250+250µA
CS- Input Bias CurrentICS-VCS+ - VCS- = 0.3V400µA
Unity-Gain BandwidthFrom (CS+ - CS-) to CS1.0MHz
REF OUTPUT BUFFERREF Output VoltageVREF-100µA ≤ IREF ≤ +100µA2.853.003.15V
DIM DRIVERVCLMP - VLO = 4V520Source CurrentVCLMP - VLO = 8V3067mA
VCLMP - VLO = 4V1022Sink CurrentVCLMP - VLO = 8V4076mA
GATE DRIVERDRI UVLO ThresholdVUVLO_THDRI rising4.04.24.4V
DRI UVLO Threshold HysteresisVUVLO_HYST0.3V
ZOUT_LVDRI = 7.0V, DRV sinking 250mA2.84Driver Output ImpedanceZOUT_HVDRI = 7.0V, DRV sourcing 250mA5.08Ω
Peak Sink CurrentISKVDRI = 7.0V2.5A
Peak Source CurrentISRVDRI = 7.0V1.4A
PWM, ILIM, AND HICCUP COMPARATORPWM Comparator Offset VoltageVCOMP - (VSNS+ - VSNS-)0.7V
Peak Current-Limit Comparator
Trip Threshold160200240mV
Peak Current-Limit Comparator
Propagation Delay (Excluding
Blanking Time)
50mV overdrive40ns
HICCUP Comparator Trip
Threshold235300385mV
SNS+ Input Bias CurrentVSNS+ = 0V, VSNS- = 0V-100-65µA
SNS- Input Bias CurrentVSNS+ = 0V, VSNS- = 0V-100-65µA
Blanking TimetBLNK40ns
ELECTRICAL CHARACTERISTICS (continued)(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 1µF, CCLMP= 0.1µF, RT= 25kΩ, TA= TJ = -40°C to +125°C, unless otherwise noted.
Typical specifications are at TA= +25°C.)
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
ELECTRICAL CHARACTERISTICS (continued)(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 1µF, CCLMP= 0.1µF, RT= 25kΩ, TA= TJ = -40°C to +125°C, unless otherwise noted.
Typical specifications are at TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
ERROR AMPLIFIERFB Input Bias Current-100+100nA
EAMP Output Sink CurrentVFB = 1.735V, VCOMP = 1V37mA
EAMP Output Source CurrentVFB = 0.735V, VCOMP = 1V27mA
EAMP Input Common-Mode
Voltage03.0V
EAMP Output Clamp Voltage1.11.72.4V
Voltage GainAVRCOMP = 100kΩ to AGND80dB
Unity-Gain BandwidthGBWRCOMP = 100kΩ to AGND, CCOMP = 100pF
to AGND0.5MHz
OSCILLATOR, OSC SYNC, CLK, AND CLKOUTfSWMIN125RTSYNC Frequency RangefSWMAX500kHz
RT = 25kΩ475500525RTSYNC Oscillator FrequencyRT = 100kΩ106125143kHz
RTSYNC High-Level VoltageVSIHL2.8V
RTSYNC Low-Level VoltageVSILL0.4V
CLKOUT High LevelISINK = 0.8mA2.8V
CLKOUT Low LevelISOURCE = 1.6mA0.4V
CLKOUT Maximum Load
CapacitanceCCLK_CAPfSW = 500kHz500pF
DIM SYNC, DIM RAMP, AND DIM PWM GENInternal Ramp FrequencyfRAMP160200240Hz
External Sync Frequency RangefDIM802000Hz
External Sync Low-Level VoltageVLTH0.4V
External Sync High-Level VoltageVHTH3.2V
DIM Comparator OffsetVDIMOS170200300mV
DIGITAL SOFT-STARTSoft-Start DurationtSS4.0ms
OVERVOLTAGE COMPARATOR, LOAD OVERCURRENT COMPARATOROVP Overvoltage Comparator
ThresholdVOVVOV rising1.201.2351.27V
OVP Overvoltage Comparator
HysteresisVOV_HYST63.5mV
SLOPE COMPENSATIONSlope Compensation Peak
Voltage Per CycleClock generated by RT120mV
Slope CompensationExternal clock applied to RTSYNC15mV/µs
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
THERMAL SHUTDOWNThermal Shutdown TemperatureTSHDNTemperature rising+165°C
Hysteresis∆TSHDN20°C
ELECTRICAL CHARACTERISTICS (continued)(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 1µF, CCLMP= 0.1µF, RT= 25kΩ, TA= TJ = -40°C to +125°C, unless otherwise noted.
Typical specifications are at TA= +25°C.)
Note 1:Dropout voltage is defined as the input to output differential voltage at which the regulator output voltage drops 100mV below
the nominal output voltage.
Note 2:VCLMPTHdetermines the voltage required to operate the current-sense amplifier. The DIM driver requires 2.5V for (VCLMP- VLO)
to drive the external MOSFET. VHIis typically one diode drop above VCLMP. A large capacitor connected to VCLMPslows the
response of the LED current-sense circuitry, resulting in current overshoot. To ensure proper operation, connect a 0.1µF
capacitor from CLMP to LO.
Typical Operating Characteristics(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 10µF, CCLMP= 0.1µF, RT= 25kΩ, RCS= 0.1Ω, TA= +25°C, unless otherwise noted.)
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX16831 toc01
TEMPERATURE (°C)
SHUTDOWN CURRENT (
OPERATING CURRENT
vs. TEMPERATURE
MAX16831 toc02
TEMPERATURE (°C)
OPERATING CURRENT (mA)
DGT AND DRV NOT
SWITCHING
VOLTAGE ACROSS LED CURRENT-SENSE
RESISTOR vs. SUPPLY VOLTAGE
MAX16831 toc03
SUPPLY VOLTAGE (V)
VOLTAGE ACROSS R
(mV)
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
Typical Operating Characteristics (continued)(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 10µF, CCLMP= 0.1µF, RT= 25kΩ, RCS= 0.1Ω, TA= +25°C, unless otherwise noted.)
REG2 OUTPUT VOLTAGE
vs. TEMPERATURE
MAX16831 toc04
TEMPERATURE (°C)
REG2 OUTPUT VOLTAGE (V)
IREG2 = 20mA
REG2 OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX16831 toc05
SUPPLY VOLTAGE (V)
REG2 OUTPUT VOLTAGE (V)
IREG2 = 20mA
REG1 OUTPUT VOLTAGE
vs. TEMPERATURE
MAX16831 toc06
TEMPERATURE (°C)
REG1 OUTPUT VOLTAGE (V)
IREG1 = 2mA
REG1 OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX16831 toc07
SUPPLY VOLTAGE (V)
REG1 OUTPUT VOLTAGE (V)
IREG1 = 2mA
CLMP REGULATOR VOLTAGE
vs. TEMPERATURE
MAX16831 toc08
TEMPERATURE (°C)
CLMP VOLTAGE (V)
VHI - VLO = 11V
CLMP VOLTAGE = VCLMP - VLO
CLMP REGULATOR VOLTAGE
vs. (VHI - VLO)
MAX16831 toc09
VHI - VLO (V)
CLMP REGULATOR VOLTAGE (V)
CLMP REGULATOR VOLTAGE = VCLMP - VLO
REF OUTPUT VOLTAGE
vs. TEMPERATURE
MAX16831 toc10
REF OUTPUT VOLTAGE (V)
IREF = 100µA
REF OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX16831 toc11
REF OUTPUT VOLTAGE (V)
PWM OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX16831 toc12
PWM FREQUENCY (kHz)
RT = 25kΩ
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
Typical Operating Characteristics (continued)(VCC= VUVEN= 14V, CREG1= 1µF, CREG2= 10µF, CCLMP= 0.1µF, RT= 25kΩ, RCS= 0.1Ω, TA= +25°C, unless otherwise noted.)
PWM OSCILLATOR FREQUENCY
vs. 1/RT CONDUCTANCE
MAX16831 toc13
1/RT (kΩ-1)
PWM FREQUENCY (kHz)
2ms/div
200Hz DIMMING OPERATION10% DIMMING
1A/div
MAX16831 toc14
50% DIMMING
1A/div
90% DIMMING
1A/div
LED CURRENT DUTY CYCLE
vs. DIM VOLTAGE
MAX16831 toc15
DIM VOLTAGE (V)
LED CURRENT DUTY CYCLE (%)20
40ns/div
DRIVER (DRV) RISE TIMEDRV OUTPUT
RISING
MAX16831 toc16
2V/div
5nF CAPACITOR CONNECTED
FROM DRV TO AGND
40ns/div
DRIVER (DRV) FALL TIMEDRV OUTPUT
FALLING
MAX16831 toc17
2V/div
5nF CAPACITOR CONNECTED
FROM DRV TO AGND
40ns/div
DGT RISE TIMEDGT OUTPUT
RISING
14V OFFSET
MAX16831 toc18
2V/div
14V
VHI - VLO = 11V
1nF CAPACITOR CONNECTED
FROM DGT TO AGND
40ns/div
DGT FALL TIMEDGT OUTPUT
FALLING
14V OFFSET
MAX16831 toc19
2V/div
14V
VHI - VLO = 11V
1nF CAPACITOR CONNECTED
FROM DGT TO AGND
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
Pin Description
PINNAMEFUNCTION1, 24N.C.No Connection. Not internally connected.UVEN
Undervoltage Lockout (UVLO) Threshold/Enable Input. UVEN is a dual-function adjustable UVLO
threshold input with an enable feature. Connect UVEN to VCC through a resistive voltage-divider to
program the UVLO threshold. Connect UVEN directly to VCC to use the 6.0V (max) default UVLO
threshold. Apply a voltage greater than 1.244V to UVEN to enable the device.REG1
5V Regulator Output. REG1 is an internal low-dropout voltage regulator that generates a 5V (VCC >
6V) output voltage and supplies power to internal circuitry. Bypass REG1 to AGND through a 1µF
ceramic capacitor.AGNDAnalog GroundREFAccurate 3V Buffered Reference Output. Connect REF to DIM through a resistive voltage-divider to
apply a DC voltage for analog-controlled dimming functionality. Leave REF unconnected if unused.DIM
Dimming Control Input. Connect DIM to an external PWM signal for PWM dimming. For analog-
controlled dimming, connect DIM to REF through a resistive voltage-divider. The dimming frequency
is 200Hz under these conditions. Connect DIM to AGND to turn off the LEDs.RTSYNC
SYNC Input/Output. The PWM clock is generated by the RTSYNC oscillator. Connect an external
resistor to RTSYNC to select a clock switching frequency from 125kHz to 600kHz or connect RTSYNC
to an external clock to synchronize the MAX16831 with a master clock signal.CLKOUTClock Output. CLKOUT buffers the oscillator/clock. Connect CLKOUT to the SYNC input of another
device to operate the MAX16831 in a multichannel configuration. CLKOUT is a logic output.
9, 10, 11I.C.Internally Connected. Must be connected to AGND.COMPError-Amplifier Output. Connect the compensation network from COMP to FB for stable closed-loop
control. Use low-leakage ceramic capacitors in the feedback network.CS
Current-Sense Amplifier Output. The current-sense amplifier (CSA) senses the differential voltage
across the load sense resistor, RCS, and generates a voltage, VCS, at CS proportional to the LED
current. Connect the proper compensation resistor from CS to FB.FBError-Amplifier Inverting InputOV
Overvoltage Protection Input. Connect OV to HI through a resistive voltage-divider to set the
overvoltage limit for the load. When the voltage at OV exceeds the 1.235V (typ) threshold, an
overvoltage fault is generated and the switching MOSFET turns off. The MOSFET is turned on again
when the voltage at OV drops below 1.17V (typ).
16, 17SGNDSwitching Ground. SGND is the ground for non-analog and high-current gate driver circuitry.DRVGate Driver Output. Connect DRV to the gate of an external n-channel MOSFET for switching.DRIGate Driver Supply Input. Connect DRI to REG2 to power the primary switching MOSFET driver.
Bypass DRI to AGND through a 10µF ceramic capacitor.SNS+Positive Peak Current-Sense Input. Connect SNS+ to the positive side of the switch current-sense
resistor, RSENSE.SNS-Negative Peak Current-Sense Input. Connect SNS- to the negative side of the switch current-sense
resistor, RSENSE.QGNDAnalog Ground. Ensure a low-impedance connection between QGND and AGND.DGTDimming Gate Driver Output. Connect DGT to the gate of an external n-channel MOSFET for
dimming. DGT is powered by the internal regulator, CLMP, and is referenced to LO.
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
Detailed DescriptionThe MAX16831 is a current-mode PWM LED driver
used for driving HBLEDs. By using two current regula-
tion loops, 5% output current accuracy is achieved.
One current regulation loop controls the external
switching MOSFET peak current through a sense resis-
tor, RSENSE, from SNS+ to SNS-, while the other current
regulation loop controls the average LED string current
through the sense resistor RCSin series with the LEDs.
The wide operating supply range of (6.0V/5.5V
ON/OFF) up to 76V makes the MAX16831 ideal in auto-
motive applications.
The MAX16831 features a programmable undervoltage
lockout (UVEN) that ensures predictable operation dur-
ing brownout conditions. The input UVEN circuit monitors
the supply voltage, VCC, and turns the driver off when
VCCdrops below the UVLO threshold. Connect UVEN to
MAX16831 includes a cycle-by-cycle current limit that
turns off the gate drive to the external switching MOS-
FET (QS) during an overcurrent condition. The
MAX16831 features a programmable oscillator that sim-
plifies and optimizes the design of external magnetics.
The MAX16831 includes three internal voltage regula-
tors, REG1, REG2, and CLMP, and a 3V buffered refer-
ence output, REF. Connect REG2 to the driver supply,
DRI, to power the switching MOSFET driver.
The MAX16831 is capable of synchronizing with an
external clock or operating in stand-alone mode. A sin-
gle resistor, RT, can be used to adjust the switching fre-
quency from 125kHz to 600kHz for stand-alone
operation. To synchronize the device with an external
clock, apply a clock signal directly to the RTSYNC
input. A buffered clock output, CLKOUT, is available to
configure the MAX16831 in multichannel applications.
Pin Description (continued)
PINNAMEFUNCTIONLO
Low-Voltage Input. LO is the return point for the LED current. When using the MAX16831 in a buck-
boost configuration, connect LO to VCC. When using the device in a boost configuration only,
connect LO to SGND. Connect LO to the junction of the inductor and LED current-sense resistor,
RCS, when using a buck configuration.CS+Noninverting Current-Sense Amplifier Input. Connect CS+ to the positive side of an external sense
resistor, RCS, connected in series with the load (LEDs).CS-Inverting Current-Sense Amplifier Input. Connect CS- to the negative side of an external sense
resistor, RCS, connected in series with the load (LEDs).CLMP
Internal CLMP Regulator Output. CLMP supplies an 8V (typ) output when VHI ≥ 9V. If VHI is lower than
9V, VCLMP is one diode drop below VHI. The CLMP regulator powers the current-sense amplifier and
provides the high reference for the dimming driver. VCLMP must be at least 2.5V higher than VLO to
enable the current-sense amplifier and dimming MOSFET driver. Bypass CLMP to LO with a 0.1µF
ceramic capacitor.HIHigh-Voltage Input. HI is referred to LO. HI supplies power to the current-sense amplifier and
dimming MOSFET gate driver through the CLMP regulator.REG2
Internal Regulator Output. REG2 is an internal voltage regulator that generates a 7V output and
supplies power to internal circuitry. Connect REG2 to DRI to power the switching MOSFET driver
during normal operation. Bypass REG2 to AGND with a 10µF ceramic capacitor.VCCSupply Voltage InputI.C.
Internally Connected. This pin is internally pulled to REG1 through a 10kΩ resistor. Leave this pin
unconnected or connect it to QGND using a resistor of any value. If it is directly connected to QGND,
400µA to 600µA of current will flow out of this pin from VCC. Any resistor between this pin and QGND
will reduce the current accordingly.
—EPExposed Pad. Connect EP to AGND. EP also functions as a heatsink to maximize thermal dissipation.
Do not use as a ground connection.
MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming ControlThe MAX16831 features a differential high-side level
shifter to drive an external n-channel MOSFET for dim-
ming. Wide contrast “pulsed” dimming (1000:1) is pos-
sible by applying either a low-frequency PWM input
signal or a DC voltage to the dimming input (DIM).
Protection features include peak current limiting,
HICCUP mode current limiting, output overvoltage pro-
tection, short-circuit protection, and thermal shutdown.
The HICCUP current-limit circuitry reduces the power
delivered to the load during severe fault conditions.
Nonlatching overvoltage protection limits the voltage on
the external switching MOSFET (QS) under open-circuit
conditions in the LED string. During continuous opera-
tion at high input voltages, the power dissipation of the
MAX16831 could exceed the maximum rating and an
internal thermal shutdown circuitry safely turns off the
MAX16831 when the device junction temperature
exceeds +165°C. When the junction temperature drops
below the hysteresis temperature, the MAX16831 auto-
matically re-initiates startup.
Undervoltage Lockout/EnableThe MAX16831 features a dual-purpose adjustable
UVLO input and enable function. Connect UVEN to VCC
through a resistive voltage-divider to set the undervolt-
age lockout (UVLO) threshold. The MAX16831 is
enabled when the UVEN exceeds the 1.244V (typ)
threshold. Drive UVEN to ground to disable the output.
Setting the UVLO ThresholdThe MAX16831 features a programmable UVLO thresh-
old. Connect UVEN directly to VCCto select the default
6.0V (max) UVLO threshold. Connect UVEN to VCC
through a resistive voltage-divider to select a UVLO
threshold (Figure 1). Calculate resistor values as follows:
where RUV1+ RUV2≤270kΩ, VUVENis the 1.244V (typ)
threshold voltage, and VUVLOis the desired UVLO
threshold in volts at VCC(Figure 1).
The capacitor, CUVEN, is required to prevent chattering
at the UVLO threshold due to line impedance drops
during power-up and dimming. If the undervoltage set-
ting is very close to the required minimum operating
voltage, then there can be jumps in the voltage at VCC
during dimming, which may cause the MAX16831 to
turn on and off when the dimming signal transitions
from low to high. The capacitor, CUVEN, should be
large enough to limit the ripple on UVEN to less than
the 100mV (min) UVEN hysteresis so that the device
does not turn off under these circumstances.
Soft-StartThe MAX16831 includes a factory-set 4ms (typ) soft-
start delay that allows the load current to ramp up in a
controlled manner, minimizing output overshoot. Soft-
start begins once the device is enabled and VCC
exceeds the UVLO threshold. Soft-start circuitry slowly
increases the internal soft-start voltage, VSS, resulting
in a controlled rise of the load current. Signals applied
to DIM are ignored until the soft-start duration is com-
plete and a successive delay of 200µs has elapsed.
Internal RegulatorsThe MAX16831 includes a fixed 5V voltage regulator
REG1, a 7V voltage regulator REG2, and an internal 8V
regulator CLMP. REG1 and REG2 power up when VCC
exceeds the UVLO threshold. REG1 supplies power to
internal circuitry and remains on during PWM dimming.
It is capable of driving external loads up to 2mA.
REG2 is capable of delivering up to 20mA of current.
Connect REG2 to DRI to generate the supply voltage
for the primary switching MOSFET driver, DRV.
CLMP is powered by HI and supplies power to the cur-
rent-sense amplifier (CSA). CSA is enabled when
VCLMPgoes 2.5V above VLOand is disabled when
(VCLMP - VLO) falls below 2.28V. The CLMP regulator
also provides power to the dimming MOSFET control
circuitry. CLMP is the output of the CLMP regulator. Do
not use CLMP to power external circuitry. Bypass
CLMP to LO with a 0.1µF ceramic capacitor. A larger
capacitor will result in overshoots of the load current.VUVUVUVEN
UVLOUVEN12=×-
MAX16831
VCC
UVEN
QGND
RUV2
RUV1CUVEN
VIN
Figure 1. Setting the UVLO Threshold
