MAX16834AUP+T ,High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driverfeatures include external enable/ BOOST LED DRIVERdisable input, an on-chip oscillator, fault indic ..
MAX16835ATE+ ,High-Voltage, 350mA, Adjustable Linear High-Brightness LED DriverFeatures♦ +6.5V to +40V Operating RangeThe MAX16835 current regulator operates from a 6.5Vto 40V in ..
MAX16835ATE+ ,High-Voltage, 350mA, Adjustable Linear High-Brightness LED DriverApplications5mm x 5mm, 16-Pin TQFN Package♦ -40°C to +125°C Operating Temperature RangeAutomotive I ..
MAX16835ATE+T ,High-Voltage, 350mA, Adjustable Linear High-Brightness LED DriverELECTRICAL CHARACTERISTICS(V = V = +12V, C = 0.1µF to GND, I = 0, CS- = GND, connect R = 0.58Ω betw ..
MAX16836ASA+ ,High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V RegulatorELECTRICAL CHARACTERISTICS(V = V = +12V, C = 0.1µF to GND, I = 0, V = 0V, V = +4V, connect R = 0.58 ..
MAX16836ASA+ ,High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V RegulatorApplications 5mm x 5mm, 16-Pin TQFN Package and in 8-PinSO with Exposed Pad PackageAutomotive Inter ..
MAX4477ASA ,10 MHz, Low-noise, low-distortion, SOT23, wide-band, rail to rail op amp.MAX4475–MAX4478/MAX4488/MAX448919-2137; Rev 1; 10/02SOT23, Low-Noise, Low-Distortion, Wide-Band,Rai ..
MAX4477ASA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsELECTRICAL CHARACTERISTICS (continued)(V = +5V, V = 0V, V = 0V, V = V /2, R tied to V /2, SHDN = V ..
MAX4477ASA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Ampsapplications that require low distortion and/or♦ 10MHz GBW Product, Unity-Gain Stablelow noise. (MA ..
MAX4477ASA+T ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op Ampsapplications that require low distortion and/or♦ 10MHz GBW Product, Unity-Gain Stablelow noise. (MA ..
MAX4477ASA+T ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsFeatures♦ Low Input Voltage-Noise Density: 4.5nV/√HzThe MAX4475–MAX4478/MAX4488/MAX4489 wide-band, ..
MAX4477AUA ,SOT23 / Low-Noise / Low-Distortion / Wide-Band / Rail-to-Rail Op AmpsELECTRICAL CHARACTERISTICS(V = +5V, V = 0V, V = 0V, V = V /2, R tied to V /2, SHDN = V , T = -40°C ..
MAX16834ATP+-MAX16834ATP+T-MAX16834AUP+-MAX16834AUP+T
High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET DriverEVALUATION KIT AVAILABLE
General DescriptionThe MAX16834 is a current-mode high-brightness LED
(HB LED) driver for boost, boost-buck, SEPIC, and high-
side buck topologies. In addition to driving an n-channel
power MOSFET switch controlled by the switching con-
troller, it also drives an n-channel PWM dimming switch to
achieve LED PWM dimming. The MAX16834 integrates
all the building blocks necessary to implement a fixed-fre-
quency HB LED driver with wide-range dimming control.
The MAX16834 features constant-frequency peak cur-
rent-mode control with programmable slope compensa-
tion to control the duty cycle of the PWM controller.
A dimming driver designed to drive an external n-chan-
nel MOSFET in series with the LED string provides
wide-range dimming control up to 20kHz. In addition to
PWM dimming, the MAX16834 provides analog dim-
ming using a DC input at REFI. The programmable
switching frequency (100kHz to 1MHz) allows design
optimization for efficiency and board space reduction.
A single resistor from RT/SYNC to ground sets the
switching frequency from 100kHz to 1MHz while an
external clock signal at RT/SYNC disables the internal
oscillator and allows the MAX16834 to synchronize to
an external clock. The MAX16834’s integrated high-
side current-sense amplifier eliminates the need for a
separate high-side LED current-sense amplifier in
boost-buck applications.
The MAX16834 operates over a wide supply range of
4.75V to 28V and includes a 3A sink/source gate driver
for driving a power MOSFET in high-power LED driver
applications. It can also operate at input voltages
greater than 28V in boost configuration with an external
voltage clamp. The MAX16834 is also suitable for DC-
DC converter applications such as boost or boost-
buck. Additional features include external enable/
disable input, an on-chip oscillator, fault indicator out-
put (FLT) for LED open/short or overtemperature condi-
tions, and an overvoltage protection sense input
(OVP+) for true overvoltage protection.
The MAX16834 is available in a thermally enhanced
4mm x 4mm, 20-pin TQFN-EP package and in a thermal-
ly enhanced 20-pin TSSOP-EP package and is specified
over the automotive -40°C to +125°C temperature range.
ApplicationsSingle-String LED LCD BacklightingAutomotive Rear and Front LightingProjection System RGB LED Light SourcesArchitectural and Decorative Lighting (MR16, M111)Spot and Ambient Lights
Benefits and FeaturesIntegration Minimizes BOM for High-Brightness LED
Driver with a Wide Dimming Range Saving Space
and CostConstant-Frequency, Peak Current-Mode Control
with Programmable Slope CompensationIntegrated PWM Dimming MOSFET Driver3000:1 PWM Dimming/Analog DimmingIntegrated High-Side Current-Sense Amplifier for
LED Current Sense in Boost-Buck ConverterInternal 7V Low-Dropout RegulatorSimple Optimization for Efficiency, Board Space and
Input Operating RangeSupports Boost, Buck-Boost, SEPIC, and High-
Side Buck Topologies100kHz to 1MHz Programmable High-Frequency
OperationExternal Clock Synchronization InputWide Input Operating Voltage Range (4.75V to 28V)Works for Input Voltage > 28V with External
Voltage Clamp on VINfor Boost Converter20-Pin TQFN-EP and TSSOP-EP PackagesProtection Features Increase System ReliabilityProgrammable UVLOProgrammable True Differential Overvoltage
ProtectionFault Output (FLT) for Overvoltage, Overcurrent,
and Thermal-Warning Faults
VIN
BOOST LED DRIVERNDRV
ANALOG
DIM
OFF
DIMOUT
SENSE+
PWMDIM
PGND
LED+
LEDs
LED-
MAX16834
REFI
Simplified Application Circuit
Ordering Information and Pin Configurations appear at end
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Absolute Maximum Ratings
Electrical Characteristics(VIN= VHV= 12V, VUVEN= 5V, VLV= VPWMDIM= VSGND, CVCC= 4.7μF, CLCV= 100nF, CREF= 100nF, RSENSE+= 0.1Ω,
RRT= 10kΩ, 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.maximintegrated.com/thermal-tutorial.
IN, HV, LV to SGND................................................-0.3V to +30V
OVP+, SENSE+, DIMOUT, CLV to SGND..............-0.3V to +30V
SENSE+ to LV........................................................-0.3V to +0.3V
HV, IN to LV............................................................-0.3V to +30V
OVP+, CLV, DIMOUT to LV......................................-0.3V to +6V
PGND to SGND.....................................................-0.3V to +0.3V
VCC to SGND..........................................................-0.3V to +12V
NDRV to PGND...........................................-0.3V to (VCC+ 0.3V)
All Other Pins to SGND.............................................-0.3V to +6V
NDRV Continuous Current................................................±50mA
DIMOUT Continuous Current..............................................±2mA
VCCShort-Circuit Current to SGND Duration...........................1s
Continuous Power Dissipation (TA= +70°C)
QFN, TQFN (derate 25.6mW/°C* above +70°C).........2051mW
TSSOP (derate 26.5mW/°C above +70°C).....................2122mW
Operating Temperature Range.........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
*As per JEDEC51 standard (multilayer board).
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput Voltage RangeVIN4.7528V
Quiescent Supply CurrentIQExcluding ILED610mA
Shutdown Supply CurrentISHDNVUVEN = 0V3060μA
INTERNAL LINEAR REGULATOR (VCC)Output VoltageVCC0 ≤ ICC ≤ 50mA, 9.5V ≤ VIN ≤ 28V6.377.7V
Dropout VoltageVDOICC = 35mA (Note 2)0.651V
Short-Circuit CurrentVCC = 0V, VIN = 12V80300mA
LINEAR REGULATOR (CLV)Output Voltage(VCLV - VLV)0 ≤ ICLV ≤ 2mA, 6V ≤ VHV ≤ 28V,
6V ≤ V(HV-LV) ≤ 22V4.755.3V
Dropout VoltageVDOICLV = 2mA, 0 ≤ VLV ≤ 23.3V (Note 3)0.5V
Short-Circuit CurrentVCLV = 12V, VIN = 12V, VHV = 24V2.210mA
REFERENCE VOLTAGE (REF)Output VoltageVREF0 ≤ IREF ≤ 1mA, 4.75V ≤ VIN ≤ 28V3.6253.703.775V
REF Short-Circuit CurrentVREF = 0V30mA
UNDERVOLTAGE LOCKOUT/ENABLE INPUT (UVEN)UVEN On Threshold VoltageVUVEN_THUP1.3951.4351.475V
UVEN Threshold Voltage
Hysteresis200mV
Input Leakage CurrentILEAKVUVEN = 0V1μA
PWMDIMPWMDIM On Threshold VoltageVPWMDIM1.3951.4351.475V
Package Thermal Characteristics (Note 1)Junction-to-Ambient Thermal Resistance (θJA)
QFN, TQFN ........................................................................39°C/W
TSSOP.............................................................................37.7°C/W
Junction-to-Case Thermal Resistance (θJC)
QFN, TQFN.....................................................................6°C/W
TSSOP.............................................................................2°C/W
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSPWMDIM Threshold Voltage
Hysteresis200mV
Input Leakage CurrentVPWMDIM = 0V1μA
OSCILLATORRRT/SYNC = 5kΩ0.911.1MHzOscillator FrequencyfOSCRRT/SYNC = 25kΩ180200220kHz
Oscillator Frequency Range(Note 4)1001000kHz
External Sync Input Clock High
Threshold(Note 4)2V
External Sync Input Clock Low
Threshold(Note 4)0.4V
External Sync Input High Pulse
Width(Note 4)200ns
Maximum External Sync Period50μs
SLOPE COMPENSATION (SC)SC Pullup CurrentISCPUVSC = 100mV80100120μA
SC Discharge ResistanceRSCDVSC = 100mV8Ω
REFIREFI Input Bias CurrentVREFI = 1V1μA
REFI Input Common-Mode Range(Note 4)02V
SENSE+SENSE+ Input Bias Current(VSENSE+ - VLV) = 100mV250μA
HIGH-SIDE LED CURRENT-SENSE AMPLIFIER (VSENSE+ - VLV)Input Offset VoltageVLV > 5V, (VSENSE+ - VLV) = 5mV-2.40+2.4mV
Voltage GainAVVLV > 5V, (VSENSE+ - VLV) = 0.2V9.79.910.1V/V
(VSENSE+ - VLV) = 0.1V, no load1.8MHz3dB Bandwidth(VSENSE+ - VLV) = 0.02V, no load600kHz
LOW-SIDE LED CURRENT-SENSE AMPLIFIERInput Offset VoltageVLV < 1V, (VSENSE+ - VLV) = 0V-20+2mV
Voltage GainAVVLV < 1V, (VSENSE+ - VLV) = 0.2V9.79.910.1V/V
3dB Bandwidth600kHz
CURRENT ERROR AMPLIFIER (TRANSCONDUCTANCE AMPLIFIER)TransconductancegmVCOMP = 2V, VPWMDIM = 5V400500600μS
Open-Loop DC GainAV60dB
Input Offset Voltage-100+10mV
COMP Voltage RangeVCOMP(Note 4)0.42.5V
PWM COMPARATORInput Offset Voltage0.60.650.70V
Propagation DelaytPD50mV overdrive40ns
Electrical Characteristics (continued)(VIN= VHV= 12V, VUVEN= 5V, VLV= VPWMDIM= VSGND, CVCC= 4.7μF, CLCV= 100nF, CREF= 100nF, RSENSE+= 0.1Ω,
RRT= 10kΩ, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Electrical Characteristics (continued)(VIN= VHV= 12V, VUVEN= 5V, VLV= VPWMDIM= VSGND, CVCC= 4.7μF, CLCV= 100nF, CREF= 100nF, RSENSE+= 0.1Ω,
RRT= 10kΩ, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMinimum On-TimetON(MIN)On-time includes blanking time100ns
Duty Cycle(Note 4)9099.5%
CURRENT PEAK LIMIT COMPARATORTrip Threshold Voltage0.250.30.35V
Propagation Delay50mV overdrive with respect to NDRV40ns
OVERVOLTAGE PROTECTION INPUT (OVP+)OVP+ On Threshold VoltageVOVP_ON1.3751.4351.495V
OVP+ Hysteresis200mV
OVP+ Input Leakage Current(VOVP - VLV) = 1.235V-1+1μA
HIGH-SIDE LED SHORT COMPARATOROff ThresholdVCLV - VLV4.04.34.6V
On ThresholdVCLV - VLV4.14.44.7V
Error Reject BlankoutfOSC = 500kHz256μs
LOW-SIDE LED SHORT COMPARATOROff Threshold0.270.300.33V
Error Reject Blankout5μs
HICCUP TIMERHiccup TimefOSC = 500kHz8.2ms
GATE-DRIVER OUTPUT (NDRV)NDRV Peak Pullup CurrentVCC = 7V3A
NDRV Peak Pulldown CurrentVCC = 7V3A
p-Channel MOSFET RDSON(VCC - VNDRV) = 0.1V1.21.9Ω
n-Channel MOSFET RDSONVNDRV = 0.1V0.91.7Ω
DIMOUTDIMOUT Peak Pullup Current(VCLV - VLV) = 5V2550mA
DIMOUT Peak Pulldown Current(VCLV - VLV) = 5V2550mA
p-Channel MOSFET RDSON(VCLV - VDIMOUT) = 0.1V31Ω
n-Channel MOSFET RDSON(VDIMOUT - VLV) = 0.1V25Ω
PWMDIM to DIMOUT
Propagation Delay200ns
FAULT FLAG (FLT)FLT Pulldown CurrentVFLT = 0.2V2510mA
FLT Leakage CurrentVFLT = 1.0V1μA
Thermal Warning On Threshold+140°C
Thermal Warning Threshold
Hysteresis20°C
Note 2:Dropout voltage is defined as VIN- VCC, when VCCis 100mV below the value of VCCfor VIN= 9.5V.
Note 3:Dropout is defined as VHV- VCLV, when VCLVis 100mV below the value of VCLV for VHV= 8V.
Note 4:Not production tested. Guaranteed by design.
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
VREF vs. TEMPERATUREMAX16834 toc01
TEMPERATURE (°C)
REF
(V)
VIN = 12V
VREF vs. SUPPLY VOLTAGEMAX16834 toc02
SUPPLY VOLTAGE (V)
REF
(V)2016128
VREF vs. IREF
MAX16834 toc03
IREF (mA)
REF
(V)81235647
VIN = 12V
SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX16834 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)2016128
PWMDIM = 0
SUPPLY CURRENT
vs. TEMPERATUREMAX16834 toc05
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VIN = 12V
PWMDIM = 0
RT vs. SWITCHING FREQUENCYMAX16834 toc06
SWITCHING FREQUENCY (kHz)
RT (k
VIN = 12V
SWITCHING FREQUENCY
vs. TEMPERATUREMAX16834 toc07
TEMPERATURE (°C)
SWITCHING FREQUENCY (kHz)
VIN = 12V
VCC vs. ICCMAX16834 toc08
(V)8060702030405010
VIN = 12V
VCC vs. ICCMAX16834 toc09
ICC (mA)
(V)8070605040302010
VIN = 12VTA = +125°C
TA = +100°C
TA = +25°C
TA = -40°C
Typical Operating Characteristics(VIN= VHV= 12V, VUVEN= 5V, VLV= VPWMDIM= VSGND, CVCC= 4.7μF, CLCV= 100nF, CREF= 100nF, RSENSE+= 0.1Ω,
RRT= 10kΩ, TA= +25°C, unless otherwise noted.)
Pin Description
PINF N , T Q F N TSSOPNAMEFUNCTION3OVP+
LED-String Overvoltage Protection Input. Connect a resistive voltage-divider between the
positive output, OVP+, and LV to set the overvoltage threshold. OVP+ has a 1.435V threshold
voltage with a 200mV hysteresis.SGNDSignal GroundCOMPError-Amplifier Output. Connect an RC network from COMP to SGND for stable operation. See
the Feedback Compensation section.6REF3.7V Reference Output Voltage. Bypass REF to SGND with a 0.1μF to 0.22μF ceramic7REFICurrent Reference Input. VREFI provides a reference voltage for the current-sense amplifier to
set the LED current.SCCurrent-Mode Slope Compensation Setting. Connect to an appropriate external capacitor from
SC to SGND to generate a ramp signal for stable operation.
Typical Operating Characteristics (continued)(VIN= VHV= 12V, VUVEN= 5V, VLV= VPWMDIM= VSGND, CVCC= 4.7μF, CLCV= 100nF, CREF= 100nF, RSENSE+= 0.1Ω,
RRT= 10kΩ, TA= +25°C, unless otherwise noted.)
VCC vs. VINMAX16834 toc10
VIN (V)
(V)221814 10
TA = +125°CTA = +25°CTA = -40°C
NDRV RISE/FALL TIME
vs. CAPACITANCEMAX16834 toc11
CAPACITANCE (nF)
NDRV RISE TIME (ns)87654321
VIN = 12V
RISE TIME
FALL TIME
VCLV vs. VHVMAX16834 toc13
VHV (V)
CLV
(V)22181410
VIN = 12V
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
VCLV vs. ICLVMAX16834 toc12
ICLV (mA)
CLV
(V)
VIN = 12V
Pin Description (continued)
PINF N , T Q F N TSSOPNAMEFUNCTIONFLTActive-Low, Open-Drain Fault Indicator Output. See the Fault Indicator (FLT) section.
810RT/SYNC
Resistor-Programmable Switching Frequency Setting/Sync Control Input. Connect a resistor
from RT/SYNC to SGND to set the switching frequency. Drive RT/SYNC to synchronize the
switching frequency with an external clock.11UVEN
Undervoltage-Lockout (UVLO) Threshold/Enable Input. UVEN is a dual-function adjustable
UVLO threshold input with an enable feature. Connect UVEN to VIN through a resistive voltage-
divider to program the UVLO threshold. Observe the absolute maximum value for this pin.12PWMDIMPWM Dimming Input. Connect to an external PWM signal for dimming operation.13CSCurrent-Sense Amplifier Positive Input. Connect a resistor from CS to PGND to set the inductor
peak current limit.14PGNDPower Ground15NDRVExternal n-Channel Gate-Driver Output16VCC7V Low-Dropout Voltage Regulator. Bypass to PGND with at least a 1μF low-ESR ceramic
capacitor. VCC provides power to the n-channel gate driver (NDRV).17INPositive Power-Supply Input. Bypass to PGND with at least a 0.1μF ceramic capacitor.18HVHigh-Side Positive Supply Input Referred to LV. HV provides power to high-side linear regulator19CLV5V High-Side Regulator Output. CLV provides power to the dimming MOSFET driver. Connect a
0.1μF to 1μF ceramic capacitor from CLV to LV for stable operation.20DIMOUTExternal Dimming MOSFET Gate Driver. DIMOUT is capable of sinking/sourcing 50mA.1LVHigh-Side Reference Voltage Input. Connect to SGND for boost configuration. Connect to IN for
boost-buck configuration.2SENSE+LED Current-Sense Positive Input. Connect a bypass capacitor of at least 0.1μF between
SENSE+ and LV close to the IC.EPExposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power
dissipation. Do not use as the main IC ground connection. EP must be connected to SGND.
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Detailed DescriptionThe MAX16834 is a current-mode, high-brightness LED
(HB LED) driver designed to control a single-string LED
current regulator with two external n-channel MOSFETs.
The MAX16834 integrates all the building blocks nec-
essary to implement a fixed-frequency HB LED driver
with wide-range dimming control. The MAX16834
allows implementation of different converter topologies
such as SEPIC, boost, boost-buck, or high-side buck
current regulator.
The MAX16834 features a constant-frequency, peak-cur-
rent-mode control with programmable slope compensa-
tion to control the duty cycle of the PWM controller. A
dimming driver offers a wide-range dimming control for
the external n-channel MOSFET in series with the LED
string. In addition to PWM dimming, the MAX16834
allows for analog dimming of LED current.
The MAX16834 switching frequency (100kHz to 1MHz)
is adjustable using a single resistor from RT/SYNC. The
MAX16834 disables the internal oscillator and synchro-
nizes if an external clock is applied to RT/SYNC. The
switching MOSFET driver sinks and sources up to 3A,
making it suitable for high-power MOSFETs driving in
HB LED applications, and the dimming control allows
for wide PWM dimming at frequencies up to 20kHz.
The MAX16834 is suitable for boost and boost-buck
LED drivers (Figures 2 and 3).
The MAX16834 alone operates over a wide 4.75V to
28V supply range. With a voltage clamp that limits the
IN pin voltage to less than 28V, it can operate in boost
configuration for input voltages greater than 28V.
Additional features include external enable/disable
input, an on-chip oscillator, fault indicator output (FLT)
for LED open/short or overtemperature conditions, and
an overvoltage protection circuit for true differential
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
MAX16834
AND
128 TOSC
ERROR
REJECT
DELAY
5µs ERROR
REJECT
DELAY
4096 TOSC
HICCUP
TIMERFLTB
SENSE+
4.3V
VLVVBG
VBG
VBG
VBG
0.3V
0.6V
REFERENCE
AND
ANDAND
PWMDIM
HIGH-SIDE
REGULATOR
VBG
LDO
RAMP
GENERATOR
PWM
COMP
OSC
BLANK
5kΩ
0.3V
AV = 9.9
UVLO
REFIN
UVEN
RT/SYNC
REFI
SENSE+
COMP
PWMDIM
OVP+
VCC
NDRV
PGND
FLT
CLV
DIMOUT
INTERNAL
CIRCUITRY
CURRENT-LIMIT
COMPARATOR
LED CURRENT-
SENSE AMPLIFIERS
ERROR
AMPLIFIER
LV REFERENCE
SWITCH
NDRVB
TEMPERATURE
SENSE
VLV
VLV
FLTA
FLTB
REFHI
FLTAFLTB
VLV
VHV
VREF
VREF
LPF
VIN
VLV
REFHI
NDRVB
SGND
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
The MAX16834 is also suitable for DC-DC converter
applications such as boost or boost-buck (Figures 6
and 7). Other applications include boost LED drivers
with automotive load dump protection (Figure 4) and
high-side buck LED drivers (Figure 5).
Undervoltage Lockout/EnableThe MAX16834 features an adjustable UVLO using the
enable input (UVEN). Connect UVEN to VINthrough a
resistive divider to set the UVLO threshold. The
MAX16834 is enabled when the VUVENexceeds the
1.435V (typ) threshold. See the Setting the UVLO
Thresholdsection for more information.
UVEN also functions as an enable/disable input to the
device. Drive UVEN low to disable the output and high
to enable the output.
Reference Voltage (REF)The MAX16834 features a 3.7V reference output, REF.
REF provides power to most of the internal circuit blocks
except for the output drivers and is capable of sourcing
1mA to external circuits. Connect a 0.1μF to 0.22μF
ceramic capacitor from REF to SGND. Connect REF to
REFI through a resistive divider to set the LED current.
Reference Input (REFI)The output current is proportional to the voltage at
REFI. Applying an external DC voltage at REFI or using
a potentiometer from REF to SGND allows analog dim-
ming of the output current.
High-Side Reference Voltage Input (LV)LV is a reference input. Connect LV to SGND for boost
and SEPIC topologies. Connect LV to IN for boost-buck
and high-side buck topologies.
Dimming Driver Regulator
Input Voltage (HV)The voltage at HV provides the input voltage for the
dimming driver regulator. For boost or SEPIC topology,
connect HV either to IN or to VCC. For boost-buck, con-
nect HV to a voltage higher than IN. The voltage at HV
must not exceed 28V with respect to PGND. For the
high-side buck, connect HV to IN.
Dimming MOSFET Driver (DIMOUT)The MAX16834 requires an external n-channel MOSFET
for PWM dimming. Connect the gate of the MOSFET to
the output of the dimming driver, DIMOUT, for normal
operation. The dimming driver is capable of sinking or
sourcing up to 50mA of current.
n-Channel MOSFET Switch Driver (NDRV)The MAX16834 drives an external n-channel switching
MOSFET. NDRV swings between VCCand PGND.
NDRV is capable of sinking/sourcing 3A of peak current,
allowing the MAX16834 to switch MOSFETs in high-
power applications. The average current demanded
from the supply to drive the external MOSFET depends
on the total gate charge (QG) and the operating
frequency of the converter, fSW. Use the following equa-
tion to calculate the driver supply current INDRV
required for the switching MOSFET:
INDRV= QGx fSW
Pulse Dimming Inputs (PWMDIM)The MAX16834 offers a dimming input (PWMDIM) for
pulse-width modulating the output current. PWM dim-
ming can be achieved by driving PWMDIM with a pul-
sating voltage source. When the voltage at PWMDIM is
greater than 1.435V, the PWM dimming MOSFET turns
on and when the voltage on PWMDIM is below 1.235V,
the PWM dimming MOSFET turns off.
High-Side Linear Regulator (VCLV)The MAX16834’s 5V high-side regulator (CLV) powers
up the dimming MOSFET driver. VCLVis measured with
respect to LV and sources up to 2mA of current.
Bypass CLV to LV with a 0.1μF to 1μF low-ESR ceramic
capacitor. The maximum voltage on CLV with respect
to PGND must not exceed 28V. This limits the input volt-
age for boost-buck topology.
Low-Side Linear Regulator (VCC)The MAX16834’s 7V low-side linear regulator (VCC) pow-
ers up the switching MOSFET driver with sourcing capa-
bility of up to 50mA. Use at least a 1μF low-ESR ceramic
capacitor from VCCto PGND for stable operation.
LED Current-Sense Input (SENSE+)The differential voltage from SENSE+ to LV is fed to an
internal current-sense amplifier. This amplified signal is
then connected to the negative input of the transcon-
ductance error amplifier. The voltage gain factor of this
amplifier is 9.9 (typ).
Whenever VLVis greater than 5V, the input impedance
of the LED current-sense amplifier seen at the SENSE+
pin is 1kΩ±30%. In that condition, a bias current of
20μA (±30%) is pulled from SENSE+, in addition to the
current due to the 1kΩresistor. When VLVis less than
1V, the amplifier input (SENSE+ pin) is in high imped-
ance and the bias current of 20μA (±30%) is pushed
out of that pin.
Always have a bypass capacitor of at least 0.1μF value
between SENSE+ and LV and close to the IC.
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Internal Transconductance Error AmplifierThe MAX16834 has a built-in transconductance amplifi-
er used to amplify the error signal inside the feedback
loop. The amplified current-sense signal is connected
to the negative input of the gmamplifier with the current
reference connected to REFI. The output of the op amp
is controlled by the input at PWMDIM. When the signal
at PWMDIM is high, the output of the op amp connects
to COMP; when the signal at PWMDIM is low, the out-
put of the op amp disconnects from COMP to preserve
the charge on the compensation capacitor. When the
voltage at PWMDIM goes high, the voltage on the com-
pensation capacitor forces the converter into a steady
state. COMP is connected to the negative input of the
PWM comparator with CMOS inputs, which draw very
little current from the compensation capacitor at COMP
and thus prevent discharge of the compensation
capacitor when the PWMDIM input is low.
Internal OscillatorThe internal oscillator of the MAX16834 is programma-
ble from 100kHz to 1MHz using a single resistor at
RT/SYNC. Use the following formula to calculate the
switching frequency:
where RT is the resistor from RT/SYNC to SGND.
The MAX16834 synchronizes to an external clock signal
at RT/SYNC. The application of an external clock dis-
ables the internal oscillator allowing the MAX16834 to
use the external clock for switching operation. The
internal oscillator is enabled if the external clock is
absent for more than 50μs. The synchronizing pulse
minimum width for proper synchronization is 200ns.
Switching MOSFET
Current-Sense Input (CS)CS is part of the current-mode control loop. The switch-
ing control uses the voltage on CS, set by RCS, to termi-
nate the on pulse width of the switching cycle, thus
achieving peak current-mode control. Internal leading-
edge blanking is provided to prevent premature turn-off
of the switching MOSFET in each switching cycle.
Slope Compensation (SC)The MAX16834 uses an internal-ramp generator for
slope compensation. The ramp signal also resets at the
beginning of each cycle and slews at the rate pro-
grammed by the external capacitor connected at SC.
The current source charging the capacitor is 100μA.
Overvoltage Protection (OVP+)OVP+ sets the overvoltage threshold limit across the
LEDs. Use a resistive divider between output OVP+
and LV to set the overvoltage threshold limit. An internal
overvoltage protection comparator senses the differen-
tial voltage across OVP+ and LV. If the differential volt-
age is greater than 1.435V, NDRV is disabled and FLT
asserts. When the differential voltage drops by 200mV,
NDRV is enabled and FLTdeasserts. The PWM dim-
ming MOSFET is still controlled by the PWMDIM input.
Fault Indicator (FLT)The MAX16834 features an active-low, open-drain fault
indicator (FLT). FLTasserts when one of the following
occurs:Overvoltage across the LED stringShort-circuit condition across the LED string, orOvertemperature condition
When the output voltage drops below the overvoltage
set point minus the hysteresis, FLTdeasserts. Similarly
during the short-circuit period, the fault signal
deasserts when the dimming MOSFET is on, which
happens every hiccup cycle during short circuit. During
overtemperature fault, the FLTsignal is the inverse of
the PWM input.
Applications Information
Setting the UVLO ThresholdThe UVLO threshold is set by resistors R1 and R2 (see
Figure 2). The MAX16834 turns on when the voltage
across R2 exceeds 1.435V, the UVLO threshold. Use
the following equation to set the desired UVLO thresh-
old:
In a typical application, use a 10kΩresistor for R2 and
then calculate R1 based on the desired UVLO threshold.
Setting the Overvoltage ThresholdThe overvoltage threshold is set by resistors R4 and R9
(see Figure 2). The overvoltage circuit in the MAX16834
is activated when the voltage on OVP+ with respect to
LV exceeds 1.435V. Use the following equation to set
the desired overvoltage threshold:RRROV=+.()1435499RRRUVEN=+.()1435122(kHz)5000k
RT(k)(kHz)OSC=×Ω
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Programming the LED CurrentThe LED current is programmed using the voltage on
REFI and the LED current-sense resistor R10 (see
Figure 2). The current is given by:
where VREFis 3.7V and the resistors R5, R6, and R10
are in ohms. The regulation voltage on the LED current-
sense resistor must not exceed 0.3V to prevent activa-
tion of the LED short-circuit protection circuit.
Boost ConfigurationIn the boost converter (Figure 2), the average inductor
current varies with the line voltage. The maximum aver-
age current occurs at the lowest line voltage. For the
boost converter, the average inductor current is equal
Calculate maximum duty cycle using the below equation.
where VLEDis the forward voltage of the LED string in
volts, VDis the forward drop of the rectifier diode D1 in
volts (approximately 0.6V), VINMINis the minimum input
supply voltage in volts, and VFETis the average drain to
source voltage of the MOSFET Q1 in volts when it is on.
Use an approximate value of 0.2V initially to calculate
DMAX. A more accurate value of the maximum duty
cycle can be calculated once the power MOSFET is
selected based on the maximum inductor current.
Use the following equations to calculate the maximum
average inductor current ILAVG, peak-to-peak inductor
current ripple ΔIL,and the peak inductor current ILPinVVVVMAX
LEDDINMIN
LEDDFET=+−−VRRALEDREF=×+×()56599().
VIN
NDRVQ1
OFF
PWMDIM
SGND
R10R8
MAX16834
FLT
DIMOUT
SENSE+
OVP+
CLV
COMP
PGND
UVEN
RT/SYNC
VCC
REF
REFI
LED+
LEDs
LED-
Figure 2. Boost LED Driver
MAX16834High-Power LED Driver with Integrated
High-Side LED Current Sense and
PWM Dimming MOSFET Driver
Allowing the peak-to-peak inductor ripple (ΔIL) to be
±30% of the average inductor current:
and
The inductance value (L) of the inductor L1 in henries
(H) is calculated as:
where fSWis the switching frequency in hertz, VINMIN
and VFETare in volts, and ΔIL is in amperes.
Choose an inductor that has a minimum inductance
greater than the calculated value. The current rating of
the inductor should be higher than ILPat the operating
temperature.
Boost-Buck ConfigurationIn the boost-buck LED driver (Figure 3), the average
inductor current is equal to the input current plus the
LED current.
Calculate maximum duty cycle using the following
equation:
where VLEDis the forward voltage of the LED string in
volts, VDis the forward drop of the rectifier diode D1
(approximately 0.6V) in volts, VINMINis the minimum
input supply voltage in volts, and VFETis the average
drain to source voltage of the MOSFET Q1 in volts when
it is on. Use an approximate value of 0.2V initially to cal-
culate DMAX. A more accurate value of maximum duty
cycle can be calculated once the power MOSFET is
selected based on the maximum inductor current.
Use the below equations to calculate the maximum
average inductor current ILAVG, peak-to-peak inductor
current ripple ΔIL, and the peak inductor current ILPin
amperes:
Allowing the peak-to-peak inductor ripple ΔILto be
±30% of the average inductor current:
The inductance value (L) of the inductor L1 in henries is
calculated as:
where fSWis the switching frequency in hertz, VINMIN
and VFETare in volts, and ΔIL is in amperes. Choose an
inductor that has a minimum inductance greater than
the calculated value.
Peak Current-Sense Resistor (R8)The value of the switch current-sense resistor R8 for the
boost and boost-buck configurations is calculated as
follows:
where 0.25V is the minimum peak current-sense thresh-
old, ILPis the peak inductor current in amperes, and
the factor 1.25 provides a 25% margin to account for
tolerances. The worst cycle-by-cycle current limiter trig-
gers at 350mV (max). The ISATof the inductor should
be higher than 0.35V/R8.
Output CapacitorThe function of the output capacitor is to reduce the
output ripple to acceptable levels. The ESR, ESL, and
the bulk capacitance of the output capacitor contribute
to the output ripple. In most applications, the output
ESR and ESL effects can be dramatically reduced by
using low-ESR ceramic capacitors. To reduce the ESL
and ESR effects, connect multiple ceramic capacitors
in parallel to achieve the required bulk capacitance. To
minimize audible noise generated by the ceramic
capacitors during PWM dimming, it may be necessary
to minimize the number of ceramic capacitors on the
output. In these cases an additional electrolytic or tan-
talum capacitor provides most of the bulk capacitance.
Boost and boost-buck configurations:The calcula-
tion of the output capacitance is the same for both
boost and boost-buck configurations. The output ripple
is caused by the ESR and the bulk capacitance of the
output capacitor if the ESL effect is considered negligi-
ble. For simplicity, assume that the contributions fromILP025
125=×)ΩVVD
INMINFETMAXL=−×
IILILI
LAVG
PAVGL××+2IAVGLED
MAX=−1VVVVMAXLEDD
LEDDINMINFET=++−VVD
INMINFETMAXL=−×ILI
PAVGL=+Δ
ΔIILLAVG=××032.IAVGLED
MAX=−1
