Analysis of switched-capacitor networks in the frequency domain using continuous-time two-port equivalents

Abstract

The proposed analysis method permits the frequency response of switched-capacitor (SC) networks by means of conventional simulation programs for continuous-time (or analog) networks. It is shown that SC networks can be decomposed into two-ports containing exclusively (passive or active) continuous-time elements and into such containing switches and capacitors. These two-ports of the latter kind can be assigned to four different classes, the basic SC structures. For each of the basic SC structures considered analog equivalent two-ports are derived exhibiting up to the Nyquist-rate equal node voltages at the discrete-time instants and equal charge transfers between the discrete-times. These equivalent twoports contain capacitors, frequency-dependent resistors, and, in some cases, a voltage-controlled current source. Hence the frequency transfer function of SC networks can be computed via the simulation of a continuous-time equivalent network. A user-ready implementation on SPICE is given and the measured results of a SC laboratory model match well with the computed predictions.