26185.301
A8431
White LED Driver Constant Current Step-up Converter
Use the following complete part numbers when ordering:
AB SO LUTE MAX I MUM RAT INGS
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
A8431 MLPD
null Output voltage up to 32 V (OVP level)
null 2.5 V to 10 V input
null Drives up to 4 LEDs at 20 mA from a 2.5 V supply
null Drives up to 5 LEDs at 20 mA from a 3 V supply
null 1.2 MHz switching frequency
null 300 mA switch current limit
null 1 µA shutdown current
null OVP pin eliminates the need for an external Zener diode on the output
FEATURES
null LED backlights
null Portable battery-powered equipment
null Cellular phones
null PDAs (Personal Digital Assistant)
null Camcorders, personal stereos, MP3 players, cameras
null Mobile GPS systems
APPLICATIONS
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.
Part Number Package Description
A8431EEH-T 6-pin, MLPD Pb-Free, Surface Mount
R
θJA
= 50 °C/W, see note 1, page 2
Approximate actual size
6
5
1
2
3 4
SW
GND
FB
VIN
OVP
EN
Preliminary Data Sheet
Subject to Change without Notice
December 7, 2004