The SM8131B is a charge pump DC/DC converter that switches between ×1and ×1.5 automatically. The SM8131B switches between ×1 and ×1.5 according to detected LED drive current, so that the battery life can be prolonged to the fullest extent. Since the connected LED are all detected for the switching, the SM8131B can respond to the variation of LED forward voltage. 6-channel of LED drive current control circuit is built-in, the SM8131B can control 1 to 6 lights of white LED, which are connected in parallel. The LED drive current per channel is set up by external resistor. Besides, by setting up SEL1/SEL2 pins, 6-channel of LED drive current control circuit can be divided to 2-groups, and input signal controlling of EN1/EN2 pins allow ON/OFF

and dimming per group.

FEATURES

■ Battery life extension by automatic charge pump switch between ×1 and ×1.5 according to the

detection of the LED drive current

■ Controlling 1 to 6 lights of white LED connected in parallel

■ Set up LED drive current value by external resistor (5kΩ:5mA/ch, 15kΩ:15mA/ch, 20kΩ:20mA/ch)

■ Dividing 6-channel to 2-groups by setting up

SEL1/SEL2 pins (L/L = 6:0ch, L/H = 5:1ch,

H/L = 4:2ch, H/H = 3:3ch)

■ 2-wire input controlling (1-wire input controlling when SEL1/SEL2 pins are set to “LOW”)

■ ON/OFF and brightness control by input signal controlling of EN1/EN2 pins

■ Supply voltage range

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

• Load current (IOUT= 120mA): 3.3 to 4.6V

■ Maximum output voltage: 4.2V (typ)

■ Maximum output current: 120mA (typ)

■ Quiescent current

• Not-switching (×1 mode): 0.7mA (typ)

• Switching (×1.5 mode): 2.0mA (typ)

■ Standby current (Power save mode): 0.01µA (typ)

■ Operating frequency (×1.5 mode): 750kHz (typ)

■ LED drive current accuracy (RSET = 20kΩ) :20mA ± 3

■ Input signal frequency for dimming (Duty = 50) :150kHz (max)

■ Package:20-pin QFN