A feedback based charge pump

Abstract

A new feedback based charge pump circuit with the controllable output voltage is proposed. By using the feedback loop and two charging channels, the output voltage can be set accurately and continuously while the input voltage is being adjusted. This technique overcomes the drawback of the traditional charge pumps which can only provide voltage that is discrete and dependent on VDD, and also alleviates the Vthn induced pumping gain loss and single charge channel induced low charging rate. A charge pump using the new circuit technique is designed and integrated into a high-speed and high-resolution A/D converter to drive a buffer. The output voltage of the charge pump ranges from 3.9V to 6.1V while the input voltage is adjusted from 0.8V to 3V. The A/D converter is fabricated in a standard 0.35-µm CMOS process technology, achieves 95.33-dBc spurious free dynamic range and 75.75-dBc signal-to-noise ratio for a 10.1-MHz input at −0.9dBFS at 100MSPS sampling rate.