White LED Driver Constant Current Step-up Converter
Description
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Preliminary Data Sheet Subject to Change without Notice April 5, 2005
A8431
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 control 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 package.
It is lead (Pb) free, with 100% matte tin leadframe plating.
White LED Driver Constant Current Step-up Converter
A8431 MLPD
Approximate actual size
SW GND FB
1 2 3
6 5 4
VIN OVP EN
RθJA = 50 °C/W, see note 1, page 2
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
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, TA.
.
–40°C to 85°C Junction Temperature, TJ(max).
150°C Storage Temperature, TS –55°C t...
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