A novel low ripple charge pump with a 2X/1.5X booster for PCM

Abstract

A low ripple switched capacitor charge pump applicable to phase change memory (PCM) is presented. For high power efficiency, the selected charge pump topology can automatically change the power conversion ratio between 2X/1.5X modes with the input voltage. For a low output ripple, a novel operation mode is used. Compared with the conventional switched capacitor charge pump, the flying capacitor of the proposed charge pump is charged to Vo − Vin during the charge phase (Vo is the prospective output voltage). In the discharge phase, the flying capacitor is placed in series with the Vin to transfer energy to the output, so the output voltage is regulated at Vo. A simulation was implemented for a DC input range of 1.6–2.1 V in on SMIC standard 40 nm CMOS process, the result shows that the new operation mode could regulate the output of about 2.5 V with a load condition from 0 to 10 mA, and the ripple voltage is lower than 4 mV. The maximum power efficiency reaches 91%.