CAT32
CMOS White LED Driver
FEATURES
s
Low quiescent ground current (0.5mA typical)
s
Power efficiency over 80%
s
Compatible pinout with LT1932
s
Adjustable output current (up to 40mA)
s
High frequency 1.2MHz operation
s
Input voltage operation down to 2.0V
s
Low resistance (0.5Ω) high voltage
Ω
H
GEN
FR
ALO
EE
LE
s
Drives up to 4 White LEDs in series
s
Shutdown current less than 1µA
A
D
F
R
E
E
TM
s
Load fault protection against open-circuits
s
Low value external components
s
Low profile (1mm) 6-lead SOT23 and TDFN
(0.8mm) package
power switch
APPLICATIONS
s
Color LCD and keypad backlighting
s
Cellular phones
s
Handheld terminals
s
Digital cameras
s
PDAs/Games
s
Portable MP3 players
DESCRIPTION
The CAT32 is a DC/DC step up converter that delivers
a regulated output current. Operation at a constant
switching frequency of 1.2MHz allows the device to be
used with very small value external inductor and ceramic
capacitors.
The CAT32 is targeted to drive multiple white light-
emitting diodes (LEDs) connected in series and provides
the necessary regulated current to control the brightness
and the color purity. An external resistor R
SET
controls
the output current level. LED currents of up to 40mA
can be supported over a wide range of input supply
voltages from 2V to 7V, making the device ideal for
battery-powered applications.
A high voltage output stage allows up to 4 White LEDs
to be driven in series. Series drive provides inherent
current matching.
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 “near zero” quiescent current.
In addition to overcurrent limiting protection, the device
also includes detection circuitry to ensure protection
against open-circuit load fault conditions.
The device is available in a low profile (1mm max height)
6-lead thin SOT23 package and in a TDFN (0.8mm max
height) package.
D1
TYPICAL APPLICATION
VIN
2.7V to 4.2V
6
VIN
1
SW
PWM
DIMMING
CONTROL
CAT32
5
SHDN
RSET
4
LED
GND
2
3
15mA
SOT23 Pin Numbers
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
© 2004 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc No. 5001, Rev. AC
CATALYST [ CATALYST SEMICONDUCTOR ]
