A Power Efficient Regulated Charge Pump Based on Charge Sharing for Contactless Devices: An Alternative to Four-Phase Charge Pumps

Abstract

In this paper, a regulated charge sharing based charge pump with boosted transfer clocks able to operate without overlapped phases for low supply voltage is presented. The overlapping period required for the threshold voltage cancellation is removed when applying the charge sharing concept to a conventional four-phase charge pump. In order to overcome this issue, transfer clocks with higher amplitude than power supply are used to control the gate of charge transfer transistors. The charge sharing based charge pump with boosted transfer clocks and the conventional four-phase charge pump are both fabricated using a 55 nm UMC High Voltage CMOS technology. Experimental measurement results reveal that the power efficiency of the charge sharing charge pump with boosted transfer clocks can be 20% higher than a traditional four-phase charge pump for an output programming current of 20 mu A. Thus, charge sharing based charge pumps are suited for low power contactless devices using an embedded NOR Flash memory for storage and code execution.