Switched-capacitor circuits with periodical nonuniform individual sampling

The operation of switched-capacitor (SC) circuits with periodical nonuniform individual sampling (PNIS) is introduced. The basic idea consists in a time averaged control of the effective rate of charge delivered by any given SC structure. In this way, the equivalent resistance of each SC branch in a circuit is individually controlled by programming the number of clock pulses in which it is active in a predetermined period of time. It is shown that this additional design degree of freedom provides a very wide programmability range in all response parameters. A second-order SC filter programmable by PNIS has been designed and fabricated in conventional CMOS technology. Experimental results are in good agreement with theoretical ones, and demonstrate the effectiveness and versatility of the proposed technique for low-frequency applications.