CAT32 Datasheet, PDF (1/14 Pages) Catalyst Semiconductor – CMOS White LED Driver

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
power switch
APPLICATIONS
s Color LCD and keypad backlighting
s Cellular phones
s Handheld terminals
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.
TYPICAL APPLICATION
VIN
2.7V to 4.2V
ALOGEN ^FR
LEA _{D F REETM}
s Drives up to 4 White LEDs in series
s Shutdown current less than 1µA
s Load fault protection against open-circuits
s Low value external components
s Low profile (1mm) 6-lead SOT23 and TDFN
(0.8mm) package
s Digital cameras
s PDAs/Games
s Portable MP3 players
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
6
1
VIN
SW
PWM
DIMMING
CONTROL
CAT32
5 _SHDN
LED ³
RSET
4
GND
2
15mA
SOT23 Pin Numbers
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
© 2004 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
Doc No. 5001, Rev. AC