Abstract
In this paper, a high-efficiency charge pump for use in CMOS image sensor(CIS) is proposed. The proposed charge pump pursues high pumping efficiency by minimizing the switching and reversion losses by taking advantage of operation characteristics of CIS. That is, the proposed charge pump minimizes the switching loss by dynamically controlling the size of clock driver, pumping capacitor, and charge transfer switch based on the operation phase of CIS pixel sensor. The charge pump also minimizes the reversion loss by guaranteeing a sufficient non-overlapping period of local clocks using a tri-state local clock driver adapting the schmitt trigger. Comparison results using a 0.13-um CMOS process technology indicate that the proposed charge pump achieves up to 49.1% reduction on power consumption under no loading current condition as compared to conventional charge pump. They also indicate that the charge pump provides 19.0% reduction on power consumption under the maximum loading current condition.
본 논문에서는 CMOS image sensor(CIS)에서 사용될 수 있는 고 효율 charge pump를 제안하였다. 제안된 charge pump는 CIS의 동작 특성을 활용하여 switching loss 및 reversion loss를 최소화하여 고 효율 동작을 실현하였다. 즉, CIS 픽셀 동작 구간에 따라 local clock driver, 펌핑 커패시터, 그리고 charge 전달 switch의 크기를 역동적으로 조절함으로써 switching loss 를 최소화하였다. 또한, schmitt trigger를 채용한 tri-state local clock driver를 이용하여 non-overlapping 구간이 충분히 확보된 local clock을 공급할 수 있게 함으로써 reversion loss를 최소화하였다. 0.13-um CMOS 공정을 이용한 시뮬레이션 비교 결과, 제안된 charge pump는 구동 전류가 없는 조건에서 기존 구조에 비해 최대 49.1% 전력 소모를 개선하였으며, 구동 전류가 최대인 조건에서는 19.0% 전력 소모를 개선할 수 있었음을 확인하였다.