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CAT4237_08 Datasheet, PDF (1/14 Pages) Catalyst Semiconductor – High Voltage CMOS Boost White LED Driver | |||
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High Voltage CMOS Boost White LED Driver
CAT4237
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
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
set by the external resistor R1. LED currents up to 40mA
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 âzeroâ quiescent current.
In addition to thermal protection and overload current
limiting, the device also enters a very low power operating
mode during âOpen LEDâ fault conditions. The device is
housed in a low profile (1mm max height) 5-lead thin
SOT23 package for space critical applications.
Part Number
Package
CAT4237TD-T3 TSOT23-5 (1)
CAT4237TD-GT3 TSOT23-5 (2)
Quantity
per Reel
3000
3000
Package
Marking
LT
UD
Notes: (1) Matte-Tin Plated Finish (RoHS-compliant).
(2) NiPdAu Plated Finish (RoHS-compliant).
PIN CONFIGURATION
5-Lead Thin SOT23
(1mm max height)
SW 1
GND 2
5 VIN
FB 3
4 SHDN
Top View
For Ordering Information details, see page 13.
TYPICAL APPLICATION CIRCUIT
VIN
L
D
VOUT
3V to
4.2V C1
33µH
C2
4.7µF
SW 0.22µF
VIN
OFF ON
CAT4237
SHDN
FB VFB = 300mV
GND
R1
15â¦
L: Sumida CDRH3D16-330
D: Central CMDSH05-4 (rated 40V)
C2: Taiyo Yuden UMK212BJ224 (rated 50V)
20mA
© Catalyst Semiconductor, Inc.
1
Characteristics subject to change without notice
Doc. No. MD-5013, Rev. B
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