CAT4238_07 Datasheet, PDF (1/14 Pages) Catalyst Semiconductor – High Efficiency 10 LED Boost Converter

High Efficiency 10 LED Boost Converter
CAT4238
FEATURES
„ Drives High Voltage LED strings (38V)
„ Up to 87% Efficiency
„ Low Quiescent Ground Current 0.6mA
„ Adjustable Output Current
„ 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
„ Portable Game Machines
ORDERING INFORMATION
DESCRIPTION
The CAT4238 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. LED currents up to 40mA can be supported over a
wide range of input supply voltages up to 5.5V, making
the device ideal for battery-powered applications. The
CAT4238 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.
Part Number
CAT4238TD-GT3
Package
TSOT23-5
Green*
Quantity Package
per Reel Marking
3000
MU
* Lead Finish NiPdAu
For Ordering Information details, see page 13.
PIN CONFIGURATION
TSOT23 5-Lead
(1mm max height)
SW 1
GND 2
FB 3
5 VIN
4 SHDN
Top View
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
TYPICAL APPLICATION CIRCUIT
VIN
C1
4.7µF
OFF ON
L
D VOUT
47µH
C2
0.22µF
SW
VIN
CAT4238
SHDN
FB ^(300mV)
GND
R1
15Ω
L: Sumida CDC5D23B-470
D: Central CMDSH05-4
C2: Taiyo Yuden UMK212BJ224 (rated 50V)
20mA
1
Doc. No. MD-5019 Rev. C