Circuit diagram for driving 4 white LEDs based on charge pump

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 ) .