LT3935

1

Rev. 0

For more information www.analog.com

TYPICAL APPLICATION

FEATURES

DESCRIPTION

36V, 4A Synchronous Step-Down LED

Driver with Silent Switcher

The LT®3935 is a monolithic, synchronous, step-down

DC/DCconverterthatutilizesfixed-frequency,peakcurrent

control and provides PWM dimming for a string of LEDs.

The LED current is programmed by an analog voltage or

the duty cycle of pulses at the CTRL pin. An output volt-

age limit can be set with a resistor divider to the FB pin.

The switching frequency is programmable from 200kHz to

2MHz by an external resistor at the RT pin or by an external

clock at the SYNC/SPRD pin. With the optional spread

spectrum frequency modulation enabled, the frequency

varies from 100% to 125% to reduce EMI.

Additional features include an LED current monitor, an

accurate EN/UVLO pin threshold, open-drain fault report-

ing for open-circuit and short-circuit load conditions,

and thermal shutdown. The LT3935 utilizes proprietary

Silent Switcher technology for very low EMI.

4A LED Driver with Fault Indication

APPLICATIONS

n

±1.5% LED Current Regulation

n

±1.2% Output Voltage Regulation

n

Spread-Spectrum Frequency Modulation

n

n

3.6V to 36V Input Voltage Range

n

0V to 36V LED String Voltage

n

200kHz to 2MHz with SYNC Function

n

20:1 Analog or Duty Cycle LED Current Control

n

Open/Short LED Fault Indication

n

Accurate LED Current Sense with Monitor Output

n

Programmable UVLO

n

Thermally Enhanced 28-Lead (5mm × 4mm) LQFN

n

Automotive Lighting

n

Industrial and General Purpose Lighting

All registered trademarks and trademarks are the property of their respective owners. Protected

by U.S. Patents including 7199560, 7321203, 9596728, 9642200 and other patents pending.

Document Feedback

30.1k

274k

45.3k

110k

10k

25m

100nF

2.2µF

2.2µF

100nF

0.1µF

×2

2.2µH

100k

30µF

10nF

EN/UVLO

CTRL

PWM

SYNC/SPRD

SS

RT

RP

ISP

ISN

FB

BST

LT3935

12V

2MHz

ISMON

FAULT

ISMON

GND

SW

10µF

3935 TA01a

6

12

18

24

30

36

70

75

80

85

90

95

100

3935 TA01b