CAT4237

© Catalyst Semiconductor, Inc.

1

Doc. No. MD-5013, Rev. B

Characteristics subject to change without notice

FEATURES

Drives 6 to 8 White LEDs in series from 3V

Up to 87% Efficiency

Low Quiescent Ground Current 0.6mA

Adjustable Output Current (up to 40mA)

High Frequency 1MHz Operation

High Voltage Power Switch

Shutdown current less than 1µA

Open LED low power mode

Automatic Shutdown at 1.9V (UVLO)

Thermal shutdown protection

RoHS-compliant

Thin SOT23 5-Lead (1mm max height)

APPLICATIONS

Color LCD and keypad Backlighting

Cellular Phones

Handheld Devices

Digital Cameras

PDAs

Portable Game Machine

ORDERING INFORMATION

Part Number

Package

Quantity

per Reel

Package

Marking

CAT4237TD-T3

TSOT23-5

(1)

3000

LT

CAT4237TD-GT3 TSOT23-5

(2)

3000

UD

Notes: (1) Matte-Tin Plated Finish (RoHS-compliant).

(2) NiPdAu Plated Finish (RoHS-compliant).

DESCRIPTION

The CAT4237 is a DC/DC step-up converter that

delivers an accurate constant current ideal for driving

LEDs. Operation at a constant 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

can be supported over a wide range of input supply

voltages from 2.8V to 5.5V, making the device ideal for

battery-powered applications. The CAT4237 high-

voltage output stage is perfect for driving six, seven or

eight white LEDs in series with inherent current matching

in LCD backlight applications.

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.

For Ordering Information details, see page 13.

PIN CONFIGURATION

TYPICAL APPLICATION CIRCUIT

5-Lead Thin SOT23

(1mm max height)

Top View

L: Sumida CDRH3D16-330

D: Central CMDSH05-4 (rated 40V)

C2: Taiyo Yuden UMK212BJ224 (rated 50V)

High Voltage CMOS Boost White LED Driver

VIN

FB

2

3

1

SHDN

5

4

SW

GND

VIN

CAT4237

LD

R1

15Ω

20mA

4.7µF

3V to

4.2V

0.22µF

FB

SHDN

SW

GND

ON

33µH

OFF