CAT4237_07 Datasheet, PDF (1/14 Pages) Catalyst Semiconductor – High Voltage CMOS Boost White LED Driver

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
Part Number
Package
Quantity
per Reel
Package
Marking
CAT4237TD TSOT23-5* 3000
LT
* Lead Finish: Matte-Tin
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 “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
5-Lead Thin SOT23
(1mm max height)
SW 1
GND 2
FB 3
5 VIN
4 SHDN
Top View
TYPICAL APPLICATION CIRCUIT
V_IN
3V to
4.2V ^C1
4.7µF
L
D
V_OUT
33µH
C₂
SW ^0.22µF
VIN
OFF ON
CAT4237
SHDN
FB ^{VFB = 300mV}
GND
R1
15Ω
20mA
© 2007 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
L: Sumida CDRH3D16-330
D: Central CMDSH05-4 (rated 40V)
C2: Taiyo Yuden UMK212BJ224 (rated 50V)
1
Doc. No. 5013, Rev. A