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AVAILABLE

EVALUATION KIT AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

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For pricing, delivery, and

ordering information, please contact Maxim Direct

at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.

General Description

The 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.

Applications

Single-String LED LCD Backlighting

Automotive Rear and Front Lighting

Projection System RGB LED Light Sources

Architectural and Decorative Lighting (MR16, M111)

Spot and Ambient Lights

DC-DC Boost/Boost-Buck Converters

Features

o Wide Input Operating Voltage Range (4.75V to 28V)

o Works for Input Voltage > 28V with External

Voltage Clamp on V

for Boost Converter

o 3000:1 PWM Dimming/Analog Dimming

o Integrated PWM Dimming MOSFET Driver

o Integrated High-Side Current-Sense Amplifier for

LED Current Sense in Boost-Buck Converter

o 100kHz to 1MHz Programmable High-Frequency

Operation

o External Clock Synchronization Input

o Programmable UVLO

o Internal 7V Low-Dropout Regulator

o Fault Output (FLT) for Overvoltage, Overcurrent,

and Thermal Warning Faults

o Programmable True Differential Overvoltage

Protection

o 20-Pin TQFN-EP and TSSOP-EP Packages

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

BOOST LED DRIVER

NDRV

ANALOG

DIM

OFF

DIMOUT

SENSE+

PWMDIM

PGND

LED+

LEDs

LED-

MAX16834

REFI

Simplified Application Circuit

Ordering Information

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

/V denotes an automotive qualified part.

/VY denotes an automotive qualified part in a “side wettable

flank” package.

PART TEMP RANGE PIN-PACKAGE

MAX16834ATP+

-40°C to +125°C

20 TQFN-EP*

MAX16834ATP/V+

-40°C to +125°C

20 TQFN-EP*

MAX16834AUP+

-40°C to +125°C

20 TSSOP-EP*

MAX16834AUP/V+

-40°C to +125°C

20 TSSOP-EP*

MAX16834AGP/VY+

-40°C to +125°C

20 QFN-EP*

Pin Configurations appear at end of data sheet.

MAX16834

19-4235; Rev 4; 8/11

Summary of content (23 pages)

PAGE 1
EVALUATION KIT AVAILABLE LE MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver AVAILAB General Description The MAX16834 is a current-mode high-brightness LED (HB LED) driver for boost, boost-buck, SEPIC, and highside buck topologies. In addition to driving an n-channel power MOSFET switch controlled by the switching controller, it also drives an n-channel PWM dimming switch to achieve LED PWM dimming.
PAGE 2
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver ABSOLUTE MAXIMUM RATINGS VCC Short-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 ......................................................
PAGE 3
MAX16834 High-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.
PAGE 4
MAX16834 High-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.) PARAMETER Minimum On-Time SYMBOL tON(MIN) Duty Cycle CONDITIONS MIN On-time includes blanking time (Note 4) TYP MAX 100 90 UNITS ns 99.5 % 0.
PAGE 5
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver 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.) VREF vs. SUPPLY VOLTAGE 3.74 3.72 3.75 VIN = 12V 3.7015 3.7010 3.70 3.68 VREF (V) 3.70 VREF (V) VREF (V) VREF vs. IREF 3.7020 MAX16834 toc02 MAX16834 toc01 3.80 MAX16834 toc03 VREF vs. TEMPERATURE 3.
PAGE 6
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver 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.) NDRV RISE/FALL TIME vs. CAPACITANCE VCC vs. VIN TA = +25°C TA = +125°C TA = -40°C 7.14 VCC (V) VIN = 12V 40 NDRV RISE TIME (ns) 7.16 50 7.12 7.10 7.08 7.06 MAX16834 toc11 7.
PAGE 7
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Pin Description (continued) PIN NAME QFN, TQFN TSSOP 7 9 8 10 9 11 10 12 11 13 CS 12 14 PGND 13 15 NDRV FLT FUNCTION Active-Low, Open-Drain Fault Indicator Output. See the Fault Indicator (FLT) section. Resistor-Programmable Switching Frequency Setting/Sync Control Input. Connect a resistor RT/SYNC from RT/SYNC to SGND to set the switching frequency.
PAGE 8
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver IN REF TO INTERNAL CIRCUITRY REFERENCE TEMPERATURE SENSE OT SGND VCC 7V LDO UVEN UVLO VBG S Q R RT/SYNC OSC SC 0.6V 5kΩ CS NDRV RAMP GENERATOR PWM COMP OR AND CURRENT-LIMIT COMPARATOR BLANK NDRVB PGND NDRVB 0.3V VREF REFI FLTB LPF AV = 9.
PAGE 9
MAX16834 High-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/Enable The MAX16834 features an adjustable UVLO using the enable input (UVEN).
PAGE 10
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Internal Transconductance Error Amplifier The MAX16834 has a built-in transconductance amplifier used to amplify the error signal inside the feedback loop. The amplified current-sense signal is connected to the negative input of the gm amplifier with the current reference connected to REFI. The output of the op amp is controlled by the input at PWMDIM.
PAGE 11
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN C1 L1 R1 LV D1 FLT LED+ C3 IN Q1 NDRV LEDs UVEN HV SC R4 CS C2 ON MAX16834 OFF PWMDIM R3 LED- RT/SYNC C5 Q2 DIMOUT R2 VCC C4 REF SENSE+ OVP+ R6 CLV R5 REFI COMP SGND PGND R8 R9 R10 C8 C7 C6 R7 Figure 2. Boost LED Driver Programming the LED Current The LED current is programmed using the voltage on REFI and the LED current-sense resistor R10 (see Figure 2).
PAGE 12
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver ILED IL AVG = 1 − D MAX Allowing the peak-to-peak inductor ripple ∆I L to be ±30% of the average inductor current: ∆IL = IL AVG × 0.3 × 2 Allowing the peak-to-peak inductor ripple (∆IL) to be ±30% of the average inductor current: ∆IL = IL AVG × 0.
PAGE 13
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN C1 L1 D1 R1 LV HV IN NDRV UVEN Q1 LEDs CS C2 SC LED+ R3 C3 ON MAX16834 R4 OFF PWMDIM LED- RT/SYNC C5 R2 VCC DIMOUT REF SENSE+ Q2 C4 R6 OVP+ R5 REFI FLT SGND CLV COMP PGND R8 R9 R10 C8 C7 C6 R7 VIN Figure 3. Boost-Buck LED Driver (VLED+ < 28V) ESR and the bulk capacitance are equal, allowing 50% of the ripple for the bulk capacitance.
PAGE 14
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver configuration, the input current is the inductor current minus the LED current. But for both configurations, the ripple current that the input filter capacitor has to supply is the same as the inductor ripple current with the condition that the output filter capacitor should be connected to ground for boost-buck configuration.
PAGE 15
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver lowing equation. The MOSFET must be mounted on a board as per manufacturer specifications to dissipate the heat. The RMS current rating of the switching MOSFET Q1 is calculated as follows for boost and boost-buck configurations: ⎛ ID RMS = ⎜ ⎝ (IL AVG ) 2 × DMAX ⎞⎟⎠ × 1.3 Rectifier Diode Use a Schottky diode as the rectifier (D1) for fast switching and to reduce power dissipation.
PAGE 16
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Boost configuration: (R LED + R10) × VLED R OUT = (R LED + R10) × ILED + VLED Boost-buck configuration: R OUT = (R LED + R10) × VLED (R LED + R10) × ILED × D MAX + VLED where RLED is the dynamic impedance (rate of change of voltage with current) of the LED string at the operating current, R10 is the LED current-sense resistor in ohms, VLED is in volts, and ILED is in amperes.
PAGE 17
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN C1 L1 Q3 R1 C8 LV FLT IN NDRV D1 LED+ D2 24V C3 Q1 LEDs UVEN HV SC R4 CS C2 ON MAX16834 OFF PWMDIM R3 LED- RT/SYNC C5 Q2 DIMOUT R2 VCC C4 REF SENSE+ OVP+ R6 CLV R5 REFI COMP SGND PGND R8 R9 R10 C9 C7 C6 R7 Figure 4.
PAGE 18
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN LED+ C1 C3 D1 L1 R1 LV HV IN NDRV Q1 VLV LEDs UVEN C2 SC R3 RT/SYNC CS ON MAX16834 OFF PWMDIM R4 LED- C5 R2 VCC C4 Q2 DIMOUT REF SENSE+ R6 OVP+ R5 REFI CLV FLT COMP SGND PGND R8 C7 R9 R10 C8 C6 R7 VLV VLV Figure 5.
PAGE 19
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN C1 L1 VOUT R1 LV FLT IN NDRV D1 Q1 UVEN C3 HV C2 SC R3 RT/SYNC C5 R4 CS MAX16834 VREF PWMDIM DIMOUT R2 VCC C4 REF SENSE+ OVP+ CLV R6 R5 REFI COMP SGND PGND OPTIONAL C6 R9 R10 C7 R8 R7 Figure 6.
PAGE 20
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver VIN C1 L1 R1 D1 LV HV IN NDRV VOUT Q1 UVEN C2 C3 SC MAX16834 R3 R4 R11 R9 R10 CS VREF RT/SYNC PWMDIM C5 R2 VCC C4 REF DIMOUT SENSE+ OVP+ R6 R5 CLV N.C. REFI COMP FLT SGND PGND C6 R7 C7 R8 VIN Figure 7.
PAGE 21
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Layout Recommendations Typically, there are two sources of noise emission in a switching power supply: high di/dt loops and high dv/dt surfaces. For example, traces that carry the drain current often form high di/dt loops.
PAGE 22
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Pin Configurations VCC NDRV PGND CS TOP VIEW IN TOP VIEW 15 14 13 12 11 + LV 1 20 DIMOUT SENSE+ 2 HV 16 10 PWMDIM CLV 17 9 UVEN 19 CLV OVP+ 3 SGND 4 18 HV MAX16834 COMP 5 DIMOUT 18 MAX16834 LV 19 *EP 3 4 5 REF REFI 1 OVP+ 2 COMP + SGND SENSE+ 20 8 RT/SYNC 7 FLT 6 SC 17 IN 16 VCC REF 6 15 NDRV REFI 7 14 PGND SC 8 13 CS FLT 9 12 PWMDIM RT/SYNC 10 11 UVEN
PAGE 23
MAX16834 High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver Revision History REVISION NUMBER REVISION DATE 0 8/08 Initial release 1 2/09 Added TSSOP package and automotive version.