An Integrated 1.2V-to-6V CMOS Charge-Pump for Electret Earphone

This work proposes a new charge pump design that achieves a high set-up ratio for electret earphone driving circuits. The voltage pumping cell is based on Cockcroft-Walton topology to achieve small area with constant MOS capacitor value under low system voltage operation. A 6-V output voltage is regulated by a PFM-based loop. This loop includes a new switched-capacitor divider as a part of the sensing circuitry. All the components are integrated in a standard 0.18 mum CMOS. Measurement results show that with 1.2 V supply, the output voltage is around 6 V with 30 mV output ripple. The maximum output driving current is up to 0.7 mA.