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Related Links:

Datasheets:
A8431: White LED Driver - Constant Current Step-Up Converter (PDF)

Selection Guides:
Power Management ICs,

Power Management ICs: Display Power and Backlight,

Power Management ICs: Switching Regulators

when this product is updated

Press Releases:
A8430 and A8431: High-Efficiency Boost Converter ICs in Ultra-Thin Package - Optimized to Drive White LEDs,

Allegro MicroSystems, Inc. to Exhibit at Portable Design China Power Management Conference

A8431
White LED Driver - Constant Current Step-Up Converter

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

Description

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.

Functional Block Diagram

Complete Part Numbers

Part Number	Package Type	RoHS Compliant	Part Composition/ RoHS Data	Temperature	Comments	Samples	Distributor Stock
A8431EEH-T	6-lead MLP	Yes	view data	-40 °C to  85 °C	new	Due to warehouse relocation, samples will be unavailable until July 14, 2008. Contact your sales rep or purchase from distributor.
A8431EEHTR-T	6-lead MLP	Yes	view data	-40 °C to  85 °C	new	Due to warehouse relocation, samples will be unavailable until July 14, 2008. Contact your sales rep or purchase from distributor.

Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system.