The SM8135A/B is a charge pump type white LED driver. It can drive 1 to 4 backlight white LED connected in parallel, making it ideal for portable devices with small LCD. The charge pump switches between ×1 bypass mode, ×1.5 and ×2 boost mode in response to LED drive current requirements. 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). Besides, the detection of switching is repeated in approx. 1sec-cycle by mode reset action, the SM8135A/B can respond to temporary variation of supply voltage. These ingenuities on switching detection can prolong the battery life to the fullest extent. Each LED drive current is controlled by a 4-channel LED drive current control circuit. The LED drive current per channel is setup by external resistor.