A Low-Ripple Charge Pump With Novel Compensator for Transient-Response Improvement in CMOS Image Sensors

This brief presents a low-ripple, fully-integrated, linear-regulated charge pump with transient-response improvement for CMOS image sensors. A compensator is proposed to accelerate the recovery of the output when an undershoot occurs. The regulated charge pump is designed with 0.11 $\mu \text{m}$ 1-poly 4-metal CMOS process and occupies an area of 0.073 mm2. According to the post-layout simulation, the worst steady-state ripple is 0.95 mV PP and the recovery time (99.9%) of the regulated output is 155 ns when the undershoot is 114 mV. The application of the compensator leads to a 78% decrease on the recovery time. When achieving similar recovery time, the area cost of the proposed topology is reduced by 49% compared to the traditional method of increasing filter capacitance. The total power dissipation of the charge pump is 1.476 mW, and the compensator only consumes 28 $\mu \text{W}$ .