OVERVIEW

The SM8134A is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in parallel and 1 flash white LED, making the device ideal for camera-equipped cellular phones. The charge pump switches between ×1 to ×1.5 boost mode in response to LED drive current requirements to extend battery life to the maximum. The boost switching occurs in response to the drive current of all the connected LED and thus supports variations in LED forward-bias voltage drop (VF). Each LED drive current is controlled by a 5-channel LED drive current control circuit. The backlight LED drive current and ON/OFF control, and flash

LED drive current and ON/OFF control are all set by 3-wire serial interface data input. Also, an under voltage lockout (UVLO) circuit is built-in to prevent incorrect operation when the battery voltage drops.

FEATURES

■ Noise reduction due to charge pump boost circuit

■ Automatic charge pump switching to conserve power

■ Drives 1 to 4 backlight white LED (30mA/ch at maximum setting)

■ Drives a flash white LED (150mA at maximum setting)

■ Backlight and flash white LED brightness adjustment

■ 3-wire serial input interface for all setting and control

■ Under voltage lockout (UVLO) circuit built-in

■ Soft start circuit built-in

■ Thermal protection circuit built-in

■ Input voltage range

• No-load current (IOUT= 0mA): 2.7 to 4.6V

• Load current (IOUT= 80mA): 3.0 to 4.6V

• Load current (IOUT= 180mA): 3.3 to 4.6V

• Load current (IOUT= 200mA): 3.4 to 4.6V

■ Quiescent current

• Not-switching (×1.0 mode): 0.3mA (typ)

• Switching (×1.5 mode): 1.7mA (typ)

■ Standby current: 0.01µA (typ)

■ Operating frequency: 750kHz (typ)

■ Maximum backlight LED current: 30mA/ch

■ Maximum flash LED current: 150mA

■ All LED total maximum current: 200mA

■ Backlight LED current matching (ILED= 20mA) : ±3

■ Flash LED current accuracy (ILED= 150mA) : ±6.7

■ Packages: 16-pin QFN

APPLICATIONS

■ Cellular phone

■ Digital still camera

■ PDA

■ Portable games