A novel charge pump architecture for driving CMOS active pixel reset

This paper presents a novel charge pump which overcomes the limitation of low image signal swing and long reset time in the four transistor CMOS active pixel image sensor. Unlike the conventional charge pumps in the literature, the output of the voltage doubler does not directly connected to the load. Alternatively, the high voltage is served as the power supply to a reference buffer. A high precision reference voltage is fed to the reference buffer. Thus, low voltage ripple is achieved with this architecture. In order to control the output voltage within the required range, a feedback loop is included. The simulation results show that with this architecture, the output of the charge pump is enhanced from 1.05V to 4.1V with ripple less than 2mV when driving a 764×524 CMOS image sensor.