A8431 Datasheet, PDF (1/10 Pages) Allegro MicroSystems – White LED Driver Constant Current Step-up Converter

A8431 ^{Preliminary Data Sheet}
Subject to Change without Notice
April 5, 2005
White LED Driver Constant Current Step-up Converter
A8431 MLPD
Approximate actual size
SW 1
GND 2
FB 3
6 VIN
5 OVP
4 EN
R_θJA = 50 °C/W, see note 1, page 2
ABSOLUTE MAXIMUM RATINGS
SW Pin ................................................–0.3 V to 36 V
OVP Pin ..............................................–0.3 V to 36 V
Remaining Pins .................................. –0.3 V to 10 V
Ambient Operating Temperature, T_A....... –40°C to 85°C
Junction Temperature, T_J(max)............................... 150°C
Storage Temperature, T_S .................... –55°C to 150°C
The A8431 is a noninverting boost dc-dc converter that provides a
programmable constant current output up to 32 V for driving white
LEDs in series.The A8431 also offers an OVP (overvoltage protection)
pin. Driving the LEDs in series ensures identical currents and uniform
brightness. Up to four white LEDs can be driven at 20 mA from a single
cell Li-ion or a multicell NiMH power source. Up to two parallel strings
of eight white LEDs can be driven at 20 mA by increasing the supply
voltage up to 10 V.
The A8431 incorporates a power switch and a feedback sense amplifier
to provide a solution with minimum external components. The output
current can be set by adjusting a single external sense resistor and can
be varied with a voltage or a filtered PWM signal when dimming con-
trol is required. The high switching frequency of 1.2 MHz allows the
use of small inductor and capacitor values.
The A8431 is provided in a 0.75 mm high, 6-pin, 2 x 3 mm MLP pack-
age. It is lead (Pb) free, with 100% matte tin leadframe plating.
FEATURES
Output voltage up to 32 V (OVP level)
2.5 V to 10 V input
Drives up to 4 LEDs at 20 mA from a 2.5 V supply
Drives up to 5 LEDs at 20 mA from a 3 V supply
1.2 MHz switching frequency
300 mA switch current limit
1 µA shutdown current
OVP pin eliminates the need for an external Zener diode on the output
APPLICATIONS
LED backlights
Portable battery-powered equipment
Cellular phones
PDAs (Personal Digital Assistant)
Camcorders, personal stereos, MP3 players, cameras
Mobile GPS systems
Use the following complete part numbers when ordering:
Part Number
A8431EEH-T
Package
6-pin, MLPD
Description
Pb-Free, Surface Mount
26185.301