CAT4240

© Catalyst Semiconductor, Inc.

1

Doc. No. MD-5026 Rev. C

Characteristics subject to change without notice

FEATURES

Switch Current Limit 750mA

Drives High Voltage LED strings (38V)

Up to 94% Efficiency

Low Quiescent Ground Current 0.6mA

1MHz Fixed Frequency Low noise Operation

Soft start “in-rush” current limiting

Shutdown current less than 1μA

Open LED Overvoltage Protection

Automatic Shutdown at 1.9V (UVLO)

Thermal overload protection

Thin SOT23 5-Lead (1mm max height)

APPLICATIONS

GPS Navigation Systems

Portable Media Players

Handheld Devices, Digital Cameras

ORDERING INFORMATION

Part Number

Package

Quantity

per Reel

Package

Marking

CAT4240TD-GT3

TSOT23-5

Green*

3000

TG

* NiPdAu Plated Finish

For Ordering Information details, see page 13.

DESCRIPTION

The CAT4240 is a DC/DC step-up converter that delivers

an accurate constant current ideal for driving LEDs.

Operation at a fixed switching frequency of 1MHz allows

the device to be used with small value external ceramic

capacitors and inductor. LEDs connected in series are

driven with a regulated current set by the external resistor

R1. The CAT4240 high-voltage output stage is perfect for

driving mid-size and large panel displays containing up to

ten white LEDs in series.

LED dimming can be done by using a DC voltage, a logic

signal, or a pulse width modulation (PWM) signal. The

shutdown input pin allows the device to be placed in

power-down mode with “zero” quiescent current.

In addition to thermal protection and overload current

limiting, the device also enters a very low power

operating mode during “Open LED” fault conditions. The

device is housed in a low profile (1mm max height) 5-lead

thin SOT23 package for space critical applications.

Pin Configuration

Typical Application Circuit

TSOT23 5-Lead

(1mm max height)

Top View

VIN

CAT4240

L1

D1

VOUT

R1

1Ω

R2

300mA

(300mV)

1µF

4.7µF/16V

8V to

16V

VIN

5V

C1

C3

C2

FB

SHDN

GND

47µH

1µF/50V

SW

1kΩ

6 Watt Boost LED Driver

L1: Sumida CDRH6D28-470

D1: Central CMSH1-40 (rated 40V)

VIN

FB

2

3

1

SHDN

5

4

SW

GND