A fully integrated charge sharing active decap scheme for power supply noise suppression

Abstract

Power supply noise has become a major challenge for proper operation of circuits with continuous scaling of CMOS technology along with supply voltage scaling. Conventional passive decoupling capacitors exhibit significant die area penalty resulting in a limited regulation effect. This paper presents a fully integrated charge-sharing-based active decap scheme for power supply noise suppression. The proposed idea is based on allocating a portion of the available passive decap to be used as an active decap that is charged up to a higher voltage and shares its boosted charge with the noisy rail upon droop detection. The proposed scheme uses a charge pump for providing the higher voltage node, as well as a detector circuit for droop detection. The system is implemented in 32 nm CMOS process, and achieves up to ~47% worst-case droop reduction with reduced ringing and settling time, at minimal area and power penalties.