An Exponent-scalable Method for Very Small Capacitance Spread and Large Time Constant of Switched-Capacitor Integrator

Abstract

For switched-capacitor (SC) integrator, an exponent-scalable method to obtain very small capacitance spread and large time constant is presented. Based on Nagaraj-89 SC integrator, an additional SC feedback branch with an extra clock phase is employed, resulting in capacitance spread to the 3rd power in z-domain transfer function. Furthermore, with (N − 2) additional SC feedback branches using (N − 2) extra clock phases, capacitance spread to the Nth power can be achieved in z-domain transfer function. Compared with previous SC integrators, this proposed exponent-scalable method is analyzed, and it is verified by simulation that larger time constant can be realized with less capacitor area. Moreover, Monte-Carlo simulation shows low relative standard deviation of time constant is also maintained.