A 4-Stage Negative Voltage Charge Pump with Randomly Selectable Parallel Switches

A charge pump generating negative voltages meant to be applied in drivers of smart window film (SWF) is proposed. More specifically, the proposed charge pump comprising 4 stages of negative charge pump and 4-phase clock generator, where the 4 stages are parallelly floorplanned to be randomly selectable by external digital signals, to generate required negative pulse train which are needed in the mode control of SWF. Post-layout simulations of the proposed design show that the a -2.85 to -15.9 V pulse train will be generated given VDD = 5 V and Vin = GND, where the switching frequency is 20 MHz, and the peak efficiency is 58%. The voltage of the output negative pulse train meets the required voltage mode range (-8 to -10 V) for SWF to demonstrate its multi-mode functions, namely transparency, tinted, or privacy modes.