An efficiency-enhanced 2X/1.5X SC charge pump with auto-adjustable output regulation for PCM

Abstract

This paper presents a 2X/1.5X switched-capacitor charge pump for phase change memory (PCM). For a 16-bitparallelism PCM, the set/reset time is more than 100 ns, and the charge pump should output a minimum 60 mA load current. The proposed charge pump can supply 4.1 V voltage and 0-60 mA current for PCM, with an input voltage range of 2.2-3.5 V. It can also automatically change the power conversion ratio between the 2X/1.5X modes according to input voltage. For the improvement of efficiency and load transient response, an auto-adjustable output regulation scheme is employed. In this scheme, two new reference voltages are introduced and compared with output voltage. Average lasting time of the enable signal changes under different load conditions. The Enable signal then controls booster’s power transistors switching to regulate output voltage. In this way, output voltage was controlled within a permissible range. The charge pump has been designed and simulated in a 40nm CMOS process. The results show maximum power efficiency in 30 mA load current is 90.73%, and conversion ratio control increases the efficiency by 23.06% in 3 V.