CAT32
CMOS White LED Driver
FEATURES
DESCRIPTION
Low quiescent ground current (0.5mA typical)
Power efficiency over 80%
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.
Compatible pinout with LT1932
Adjustable output current (up to 40mA)
High frequency 1.2MHz operation
Input voltage operation down to 2.0V
Low resistance (0.5Ω) high voltage power switch
Drives up to 4 White LEDs in series
Shutdown current less than 1µA
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 RSET 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.
Load fault protection against open-circuits
Low value external components
Low profile (1mm) TSOT-23 6-lead and TDFN
A high voltage output stage allows up to 4 White LEDs
to be driven in series. Series drive provides inherent
current matching.
8-pad (0.8mm) package
APPLICATION
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.
Color LCD and keypad backlighting
Cellular phones
Handheld terminals
Digital cameras
PDAs/Games
In addition to overcurrent limiting protection, the
device also includes detection circuitry to ensure
protection against open-circuit load fault conditions.
Portable MP3 players
For Ordering Information details, see page 14.
The device is available in a low profile (1mm max
height) 6-lead TSOT-23 package and in an 8-pad
TDFN (0.8mm max height) package.
TYPICAL APPLICATION CIRCUIT
L
1
6.8µH
D1
VIN
2.7V
to
4.2V
C1
4.7µF
6
1
VIN
SW
CAT32
PWM
DIMMING
CONTROL
5
3
C2
1µF
LED
SHDN
RSET
4
GND
2
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
15mA
R
SET
1.50kΩ
TSOT-23 Pin Numbers
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. MD-5001 Rev. AD