Novel Low-Ripple Charge Pump for Phase Chang Memory

A low ripple switched capacitor charge pump applied to phase change memory (PCM) is proposed. Compared with the conventional switched capacitor charge pump, the flying capacitor of the proposed charge pump is charged to the difference between the prospective output voltage and the input voltage during the charge phase. In the discharge phase, the flying capacitor is connected between the input and output of the charge pump to transfer energy to output, so the output is regulated at prospective voltage. This new operation mode can reduce the output ripple caused by charge redistribution. A simulation was implemented for a DC input range of 2.8~4.4V in a SMIC standard 0.18μm CMOS process. Result shows the new operation mode can regulate the output about 5V with a load condition from 0 to 10mA, the ripple voltage is lower than 3 mV and the highest power efficiency reaches 88%.