Design-for-digital-testability 30 MHz second-order Sigma-Delta modulator

Abstract

A purely digitally testable second-order Sigma-Delta modulator is presented. In the test mode, the input stage of the modulator is reconfigured to accept a repetitive Sigma-Delta modulated bit-stream as its stimulus. The proposed test scheme has a low cost, a high fault coverage, high measurement accuracy, and is able to do the at-speed tests. The experimental results show that the dynamic range measured with the digital stimulus is only 2 dB inferior to that with its analog counterpart.