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 exponentscalable 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.