Rainbow Electronics MAX16834 User Manual

General Description

The MAX16834 is a current-mode high-brightness LED
(HB LED) driver for boost, buck-boost, 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. The MAX16834 integrates
all the building blocks necessary to implement a fixed-fre­quency HB LED driver with wide-range dimming control.
The MAX16834 features constant-frequency peak cur­rent-mode control with programmable slope compensa­tion to control the duty cycle of the PWM controller.

A dimming driver designed to drive an external n-chan­nel MOSFET in series with the LED string provides
wide-range dimming control up to 20kHz. In addition to
PWM dimming, the MAX16834 provides analog dim­ming 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 high­side current-sense amplifier eliminates the need for a
separate high-side LED current-sense amplifier in
buck-boost 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. The MAX16834 is also suitable for DC-DC
converter applications such as boost or buck-boost.
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 sense input (OVP+) for true
overvoltage protection.

The MAX16834 is available in a thermally enhanced
4mm x 4mm, 20-pin TQFN-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/Buck-Boost Converters

Features

o Wide Input Operating Voltage Range (4.75V to

28V)

o 3000:1 PWM Dimming

o Analog Dimming

o Integrated PWM Dimming MOSFET Driver

o Integrated High-Side Current-Sense Amplifier for

LED Current Sense in Buck-Boost 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 Package

MAX16834

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

________________________________________________________________

Maxim Integrated Products

1

Simplified Application Circuit

Ordering Information

19-4235; Rev 0; 8/08

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-free/RoHS-compliant package.

*

EP = Exposed pad.

PART TEMP RANGE

PIN-PACKAGE

MAX16834ATP+

-40°C to +125°C 20 TQFN-EP*

Pin Configuration appears at end of data sheet.

IN

MAX16834

PWMDIM

REFI

PGND

BOOST LED DRIVER

NDRV

CS

DIMOUT

SENSE+

LED+

LEDs

LED-

V

OFF

IN

ANALOG

ON

DIM

MAX16834

High-Power LED Driver with Integrated High-Side LED
Current Sense and PWM Dimming MOSFET Driver

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= VHV= 12V, V

UVEN

= 5V, VLV= V

PWMDIM

= SGND, C

VCC

= 4.7µF, C

LCV

= 100nF, C

REF

= 100nF, R

SENSE+

= 0.1Ω,

R

RT

= 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.maxim-ic.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

V

CC

to SGND..........................................................-0.3V to +12V

NDRV to PGND...........................................-0.3V to (V

CC

+ 0.3V)

All Other Pins to SGND.............................................-0.3V to +6V

NDRV Continuous Current................................................±50mA

DIMOUT Continuous Current..............................................±2mA

V

CC

Short-Circuit Current to SGND Duration ...........................1s

Continuous Power Dissipation (T

A

= +70°C)
20-Pin TQFN 4mm x 4mm

(derate 25.6mW/°C* above +70°C) ............................2051mW

Junction-to-Ambient Thermal Resistance (

θ

JA

) (Note 1).....39°C/W

Junction-to-Case Thermal Resistance (

θ

JC

) (Note 1) ........6°C/W

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

*

As per JEDEC51 standard (multilayer board).

Input Voltage Range V

Quiescent Supply Current I

Shutdown Supply Current I

INTERNAL LINEAR REGULATOR (VCC)

Output Voltage V

Dropout Voltage V

Short-Circuit Current VCC = 0V, VIN = 12V 80 300 mA

LINEAR REGULATOR (CLV)

Output Voltage (V

Dropout Voltage V

Short-Circuit Current V

REFERENCE VOLTAGE (REF)

Output Voltage V

REF Short-Circuit Current V

UNDERVOLTAGE LOCKOUT/ENABLE INPUT (UVEN)

UVEN On Threshold Voltage V

UVEN Threshold Voltage
Hysteresis

Input Leakage Current I

PWMDIM

PWMDIM On Threshold Voltage V

PWMDIM Threshold Voltage
Hysteresis

Input Leakage Current V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

Q

SHDN

CC

OD

CLV - VLV

DO

REF

UVEN_THUP

LEAK

PWMDIM

Excluding I

V

UVEN

0 ≤ ICC ≤ 50mA, 9.5V ≤ VIN ≤ 28V 6.3 7 7.7 V

ICC = 35mA (Note 2) 0.65 1.8 V

0 ≤ I

CLV

)

6V ≤ V

I

= 2mA, 0 ≤ VLV ≤ 23.3V (Note 3) 0.5 V

CLV

= 12V, VIN = 12V, VHV = 24V 2.2 10 mA

CLV

0 ≤ I

REF

= 0 30 mA

REF

V

UVEN

PWMDIM

LED

= 0 30 60 µA

≤ 2mA, 6V ≤ VHV ≤ 28V,

≤ 22V

(HV-LV)

≤ 1mA, 4.75V ≤ VIN ≤ 28V 3.625 3.70 3.775 V

= 0 I1I µA

= 0 I1I µA

4.75 28 V

4.7 5 5.3 V

1.395 1.435 1.475 V

200 mV

1.395 1.435 1.475 V

200 mV

610mA

MAX16834

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= VHV= 12V, V

UVEN

= 5V, VLV= V

PWMDIM

= SGND, C

VCC

= 4.7µF, C

LCV

= 100nF, C

REF

= 100nF, R

SENSE+

= 0.1Ω,

R

RT

= 10kΩ, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C.)

OSCILLATOR

Oscillator Frequency f

Oscillator Frequency Range (Note 4) 100 1000 kHz

External Sync Input Clock High
Threshold

External Sync Input Clock Low
Threshold

External Sync Input High Pulse
Width

Maximum External Sync Period 50 µs

SLOPE COMPENSATION (SC)

SC Pullup Current I

SC Discharge Resistance R

REFI

REFI Input Bias Current V

REFI Input Common-Mode Range (Note 4) 0 2 V

SENSE+

SENSE+ Input Bias Current (V

HIGH-SIDE LED CURRENT-SENSE AMPLIFIER (V

Input Offset Voltage VLV > 5V, (V

Voltage Gain A

3dB Bandwidth

LOW-SIDE LED CURRENT-SENSE AMPLIFIER

Input Offset Voltage VLV < 1V, (V

Voltage Gain A

3dB Bandwidth 600 kHz

CURRENT ERROR AMPLIFIER (TRANSCONDUCTANCE AMPLIFIER)

Transconductance g

Open-Loop DC Gain A

Input Offset Voltage -10 0 +10 mV

COMP Voltage Range V

PWM COMPARATOR

Input Offset Voltage 0.6 0.65 0.70 V

Propagation Delay t

Minimum On-Time t

Duty Cycle (Note 4) 90 99.5 %

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

OSC

SCPU

SCD

V

V

m

V

COMP

PD

ON(MIN)

R

RT/SYNC

R

RT/SYNC

(Note 4) 2 V

(Note 4) 0.4 V

(Note 4) 200 ns

VSC = 100mV 80 100 120 µA

VSC = 100mV 8 Ω

REFI

VLV > 5V, (V

(V

(V

VLV < 1V, (V

V

COMP

(Note 4) 0.4 2.5 V

50mV overdrive 40 ns

On-time includes blanking time 100 ns

= 5kΩ 0.9 1 1.1 MHz
= 25kΩ 180 200 220 kHz

= 1V I1I µA

- VLV) = 100mV 250 µA

SENSE+

- VLV)

SENSE+

- VLV) = 0.1V, no load 1.8 MHz

SENSE+

- VLV) = 0.02V, no load 600 kHz

SENSE+

= 2V, V

- VLV) = 5mV -2.4 0 +2.4 mV

SENSE+

- VLV) = 0.2V 9.7 9.9 10.1 V/V

SENSE+

- VLV) = 0V -2 0 +2 mV

SENSE+

- VLV) = 0.2V 9.7 9.9 10.1 V/V

SENSE+

= 5V 400 500 600 µS

PWMDIM

60 dB

MAX16834

High-Power LED Driver with Integrated High-Side LED
Current Sense and PWM Dimming MOSFET Driver

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= VHV= 12V, V

UVEN

= 5V, VLV= V

PWMDIM

= SGND, C

VCC

= 4.7µF, C

LCV

= 100nF, C

REF

= 100nF, R

SENSE+

= 0.1Ω,

R

RT

= 10kΩ, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°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 V

HV

- V

CLV

, when V

CLV

is 100mV below the value of V

CLV

for VHV= 8V.

Note 4: Not production tested. Guaranteed by design.

CURRENT PEAK LIMIT COMPARATOR

Trip Threshold Voltage 0.25 0.3 0.35 V

Propagation Delay 50mV overdrive with respect to NDRV 40 ns

OVERVOLTAGE PROTECTION INPUT (OVP+)

OVP+ On Threshold Voltage V

OVP+ Hysteresis 200 mV

OVP+ Input Leakage Current (V

HIGH-SIDE LED SHORT COMPARATOR

Off Threshold V

On Threshold V

Error Reject Blankout f

LOW-SIDE LED SHORT COMPARATOR

Off Threshold 0.27 0.30 0.33 V

Error Reject Blankout 5µs

HICCUP TIMER

Hiccup Time f

GATE-DRIVER OUTPUT (NDRV)

NDRV Peak Pullup Current VCC = 7V 3 A

NDRV Peak Pulldown Current VCC = 7V 3 A

p-Channel MOSFET R

n-Channel MOSFET R

DIMOUT

DIMOUT Peak Pullup Current (V

DIMOUT Peak Pulldown Current (V

p-Channel MOSFET R

n-Channel MOSFET R

PWMDIM to DIMOUT
Propagation Delay

FAULT FLAG (FLT)

FLT Pulldown Current V
FLT Leakage Current V

Thermal Warning On Threshold +140 °C

Thermal Warning Threshold
Hysteresis

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DSON

DSON

DSON

DSON

OVP_ON

- VLV) = 1.235V -1 +1 µA

OVP

- V

CLV

LV

- V

CLV

LV

= 500kHz 256 µs

OSC

= 500kHz 8.2 ms

OSC

(VCC - V

V

(V

(V

NDRV

= 0.1V 0.9 1.7 Ω

NDRV

- VLV) = 5V 25 50 mA

CLV

- VLV) = 5V 25 50 mA

CLV

- V

CLV

DIMOUT

- VLV) = 0.1V 25 Ω

DIMOUT

= 0.2V 2 5 10 mA

FLT

= 1.0V I1I µA

FLT

) = 0.1V 1.2 1.9 Ω

) = 0.1V 31 Ω

1.375 1.435 1.495 V

4.0 4.3 4.6 V

4.1 4.4 4.7 V

200 ns

20 °C

MAX16834

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

_______________________________________________________________________________________ 5

V

(V)

Typical Operating Characteristics

(VIN= VHV= 12V, V

UVEN

= 5V, VLV= V

PWMDIM

= SGND, C

VCC

= 4.7µF, C

LCV

= 100nF, C

REF

= 100nF, R

SENSE+

= 0.1Ω,

R

RT

= 10kΩ, TA= +25°C, unless otherwise noted.)

V

vs. TEMPERATURE

REF

3.74

3.72

3.70

(V)

3.68

REF

V

3.66

3.64

3.62

3.60

-40 125
TEMPERATURE (°C)

VIN = 12V

11095-25 -10 5 35 50 6520 80

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

20

18

16

14

12

10

8

6

SUPPLY CURRENT (mA)

4

2

0

428

SUPPLY VOLTAGE (V)

PWMDIM = 0

242016128

3.80

3.75

MAX16834 toc01

3.70

(V)

3.65

REF

V

3.60

3.55

3.50

10

9

MAX16834 toc04

8

7

6

5

4

3

SUPPLY CURRENT (mA)

2

1

0

V

REF

428

vs. TEMPERATURE

-40 125

vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

SUPPLY CURRENT

VIN = 12V
PWMDIM = 0

TEMPERATURE (°C)

242016128

1109565 80-10 5 20 35 50-25

3.7020

3.7015

MAX16834 toc02

3.7010

3.7005

3.7000

REF

3.6995

3.6990

3.6985

3.6980

100

MAX16834 toc05

10

RT (kΩ)

1

V

vs. I

REF

010

I

(mA)

REF

RT vs. SWITCHING FREQUENCY

VIN = 12V

SWITCHING FREQUENCY (kHz)

REF

VIN = 12V

MAX16834 toc03

981 2 3 5 64 7

MAX16834 toc06

1000100

SWITCHING FREQUENCY

605
604
603
602
601
600
599
598
597
596
595
594

SWITCHING FREQUENCY (kHz)

593
592
591

590

-40 125

TEMPERATURE (°C)

VIN = 12V

1109565 80-10 5 20 35 50-25

MAX16834 toc07

7.16

7.14

7.12

7.10

7.08

7.06

(V)

7.04

CC

7.02

V

7.00

6.98

6.96

6.94

6.92

6.90
0100

vs. TEMPERATURE

VCC vs. I

ICC (mA)

CC

VIN = 12V

908060 7020 30 40 5010

MAX16834 toc08

7.2
TA = +125°C

7.1

(V)

7.0

TA = +25°C

CC

V

6.9

6.8

0100

VCC vs. I

TA = +100°C

TA = -40°C

ICC (mA)

CC

VIN = 12V

MAX16834 toc09

908070605040302010

Pin Description

MAX16834

High-Power LED Driver with Integrated High-Side LED
Current Sense and PWM Dimming MOSFET Driver

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= VHV= 12V, V

UVEN

= 5V, VLV= V

PWMDIM

= SGND, C

VCC

= 4.7µF, C

LCV

= 100nF, C

REF

= 100nF, R

SENSE+

= 0.1Ω,

R

RT

= 10kΩ, TA= +25°C, unless otherwise noted.)

VCC vs. V

IN

MAX16834 toc10

VIN (V)

V

CC

(V)

26

22

1814

10

7.02

7.04

7.06

7.08

7.10

7.12

7.14

7.16

7.18

7.20

7.00
6

TA = +125°C

TA = +25°C

TA = -40°C

NDRV RISE/FALL TIME

vs. CAPACITANCE

MAX16834 toc11

CAPACITANCE (nF)

NDRV RISE TIME (ns)

987654321

10

20

30

40

50

0

010

VIN = 12V

RISE TIME

FALL TIME

V

CLV

vs. V

HV

MAX16834 toc13

VHV (V)

V

CLV

(V)

26

22

18

14

10

5.01

5.02

5.03

5.04

5.05

5.06

5.07

5.08

5.09

5.10

5.00
6

VIN = 12V

V

CLV

vs. I

CLV

MAX16834 toc12

I

CLV

(mA)

V

CLV

(V)

4.54.03.0 3.51.0 1.5 2.0 2.50.5

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

5.50

0

05.0

VIN = 12V

PIN NAME FUNCTION

LED-String Overvoltage Protection Input. Connect a resistive voltage-divider between the positive

1 OVP+

2 SGND Signal Ground

3 COMP

4 REF 3.7V Reference Output Voltage. Bypass REF to SGND with a 0.1µF to 0.22µF ceramic capacitor.

5 REFI

6SC

output, OVP+, and LV to set the overvoltage threshold. OVP+ has a 1.435V threshold voltage with a
200mV hysteresis.

Error-Amplifier Output. Connect an RC network from COMP to SGND for stable operation. See the
Feedback Compensation section.

Current Reference Input. V

provides a reference voltage for the current-sense amplifier to set the

REFI

LED current.

Current-Mode Slope Compensation Setting. Connect to an appropriate external capacitor from SC to
SGND to generate a ramp signal for stable operation.

MAX16834

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

_______________________________________________________________________________________ 7

Pin Description (continued)

Detailed Description

The 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 nec­essary 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, buck-boost, or high-side buck
current regulator.

The MAX16834 features a constant-frequency, peak-cur­rent-mode control with programmable slope compensa­tion 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 synchro­nizes 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 buck-boost
LED drivers (Figures 2 and 3).

The MAX16834 operates over a wide 4.75V to 28V sup­ply range. 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 overvoltage protection (Figure 1).

The MAX16834 is also suitable for DC-DC converter
applications such as boost or buck-boost (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).

PIN NAME FUNCTION

7 FLT Active-Low, Open-Drain Fault Indicator Output. See the Fault Indicator (

Resistor-Programmable Switching Frequency Setting/Sync Control Input. Connect a resistor from

8 RT/SYNC

9 UVEN

10 PWMDIM PWM Dimming Input. Connect to an external PWM signal for dimming operation.

11 CS

12 PGND Power Ground

13 NDRV External n-Channel Gate-Driver Output

14 V

15 IN Positive Power-Supply Input. Bypass to PGND with at least a 0.1µF ceramic capacitor.

16 HV High-Side Positive Supply Input Referred to LV. HV provides power to high-side linear regulator CLV.

17 CLV

18 DIMOUT External Dimming MOSFET Gate Driver. DIMOUT is capable of sinking/sourcing 50mA.

19 LV

20 SENSE+ LED Current-Sense Positive Input

—EP

CC

RT/SYNC to SGND to set the switching frequency. Drive RT/SYNC to synchronize the switching
frequency with an external clock.

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.

Current-Sense Amplifier Positive Input. Connect a resistor from CS to PGND to set the inductor peak
current limit.

7V Low-Dropout Voltage Regulator. Bypass to PGND with at least a 1µF low-ESR ceramic capacitor.

provides power to the n-channel gate driver (NDRV).

V

CC

5V 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.

High-Side Reference Voltage Input. Connect to SGND for boost configuration. Connect to IN for buck­boost configuration.

Exposed 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.

FLT

) section.