Circuit based on charge pump driving 4 white LEDs

　In this circuit , the white LED driver is an adaptive charge pump based on 1x voltage mode and 1.5x voltage mode. The input of the charge pump is connected to the VIN pin and the output is connected to the VOUT pin. The charge pump has two operating modes: open loop and closed loop. In open-loop mode, the voltage at VOUT is equal to the input voltage multiplied by the gain multiple. When the charge pump operates in closed-loop mode, the voltage at VOUT is adjusted to a constant voltage value (Vreg). An internal current source controls the current to each white LED in a common-anode configuration, and the peak drive current can be programmed through an external resistor (Rset ) .