IS31LT3354

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 09/01/2011

1

40V LED DRIVER WITH EXTERNAL SWITCH

GENERAL DESCRIPTION

The IS31LT3354 is a continuous mode inductive

step-down converter, designed for driving a single LED

or multiple series connected LEDs efficiently from a

voltage source higher than the required LED voltage.

The device operates from an input supply between 6V

and 40V and provides an externally adjustable output

current of up to 2A or even higher, which is determined

by the external MOSFET and inductor.

The IS31LT3354 includes a high-side output current

sensing circuit, which uses an external resistor to set

the nominal average output current.

Output current can be adjusted linearly by applying an

external control signal to the ADJ pin. The ADJ pin will

accept either a DC voltage or a PWM waveform. This

will provide either a continuous or a gated output

current.

Applying a voltage of 0.2V or lower to the ADJ pin

turns the output off and switches the chip into a low

current standby state.

The chip is assembled in SOT23-5 package.

FEATURES



Simple low parts count



Wide input voltage range: 6V to 40V



Output Current only limited by external

component selection



High efficiency (up to 98% )



Typical 1200:1 dimming ratio



Typical 3% output current accuracy



Single pin on/off and brightness control using

DC voltage or PWM



Up to 1MHz switching frequency



Inherent open-circuit LED protection



Thermal shutdown protection circuitry

APPLICATIONS



Low voltage halogen replacement LEDs



Automotive lighting



Low voltage industrial lighting



LED back-up lighting



Illuminated sign

TYPICAL APPLICATION CIRCUIT

GND

ADJ

GATE

Rs

L1

D1

SN3354

C2

5

4

1

2

3

up to

10 LEDs

Vin(DC)=6V~40V

AP2306

C1

0.1uF

C3

Figure 1

Typical IS31LT3354 Application Schematic

 

 

 

 

 

 

 

 

 

 

Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any 

time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are 

advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products. 

Integrated  Silicon  Solution,  Inc.  does  not  recommend  the  use  of  any  of  its  products  in  life  support  applications  where  the  failure  or  malfunction  of  the 

product  can  reasonably  be  expected  to  cause  failure  of  the  life  support  system  or  to  significantly  affect  its  safety  or  effectiveness.  Products  are  not 

authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that: 

a.) the risk of injury or damage has been minimized; 

b.) the user assume all such risks; and 

c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances

SEPTEMBER 2011

IS31LT3354