A high performance regulated charge pump for USB-OTG transceiver

A high performance regulated charge pump is designed and implemented in 1.2/2.5-V 90-nm CMOS technology. The charge pump exploits two control schemes to provide stable output voltage with small ripple output voltage and high current load drivability. The first is automatic pumping current control scheme which optimizes the pumping current flowing through flying capacitor to reduce ripple voltage. The second is variable pumping frequency control scheme which changes pumping frequency by controlling a VCO. This charge pump delivers regulated 3.8-V output voltage from a supply voltage of 2.5-V with a flying capacitor of 590-nF, while providing 50-mA of load current. The area is 0.12-mm²; and the measured output ripple voltage is less than 20-mV with a 2.2-μF load capacitor. The power efficiency is greater than 80% at the range of load current from 10 to 10-mA.