A novel low-ripple charge pump for PCM

A switched capacitor charge pump applicable to phase change memory(PCM) is presented, which can provide a extra low ripple DC output of 5V with a maximum load condition of 10mA. For low output ripple and high power effiency, 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-VDD instead of VDD during the charge period(Vo is the prospective output voltage).In the discharge period, the flying capacitor is placed in series with the VDD to transfer energy to output, so the output voltage is regulated at Vo. A simulation was implemented for a DC input range of 2.8–4.4V in a SMIC standard 0.18um CMOS process, the result shows the new operation mode could regulate the output about 5V with a load conditon from 0 to 10mA, and the ripple voltage is lower than 3mV. The higest power effiency reaches 88%.