CAT4237
High Voltage CMOS Boost White LED Driver
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)
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 R
1
. 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 “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.
APPLICATIONS
Color LCD and keypad Backlighting
Cellular Phones
Handheld Devices
Digital Cameras
PDAs
Portable Game Machine
ORDERING INFORMATION
Part Number
CAT4237TD-T3
Package
TSOT23-5
(1)
Quantity
per Reel
3000
3000
Package
Marking
LT
UD
CAT4237TD-GT3 TSOT23-5
(2)
Notes:
(1) Matte-Tin Plated Finish (RoHS-compliant).
(2) NiPdAu Plated Finish (RoHS-compliant).
PIN CONFIGURATION
5-Lead Thin SOT23
(1mm max height)
TYPICAL APPLICATION CIRCUIT
V
IN
3V to
4.2V
C
1
VIN
4
SHDN
L
33µH
D
C
2
SW 0.22µF
V
OUT
SW
1
GND
2
FB
3
5
VIN
4.7µF
CAT4237
OFF ON
SHDN
GND
L: Sumida CDRH3D16-330
D: Central CMDSH05-4 (rated 40V)
C2: Taiyo Yuden UMK212BJ224 (rated 50V)
FB
V
FB
= 300mV
R1
15Ω
20mA
Top View
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. MD-5013, Rev. B
CATALYST [ CATALYST SEMICONDUCTOR ]
