CAT32_08 Datasheet, PDF (1/14 Pages) Catalyst Semiconductor – CMOS White LED Driver

CMOS White LED Driver
CAT32
FEATURES
„ Low quiescent ground current (0.5mA typical)
„ Power efficiency over 80%
„ 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
„ Load fault protection against open-circuits
„ Low value external components
„ Low profile (1mm) TSOT-23 6-lead and TDFN
8-pad (0.8mm) package
APPLICATION
„ Color LCD and keypad backlighting
„ Cellular phones
„ Handheld terminals
„ Digital cameras
„ PDAs/Games
„ Portable MP3 players
For Ordering Information details, see page 14.
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 TSOT-23 package and in an 8-pad
TDFN (0.8mm max height) package.
TYPICAL APPLICATION CIRCUIT
L₁
6.8µH
D1
VIN
2.7V
to
4.2V
C1
4.7µF
6
1
VIN
SW
TSOT-23 Pin Numbers
PWM
DIMMING
CONTROL
CAT32
5 _SHDN
LED ³
RSET
4
R_SET
1.50kΩ
GND
2
15mA
C2
1µF
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
© Catalyst Semiconductor, Inc.
1
Characteristics subject to change without notice
Doc. No. MD-5001 Rev. AD