A digital BIST for opamps embedded in mixed-signal circuits by analysing the transient response

Abstract

A new digital BIST for OAs embedded in mixed-signal circuits is proposed in this paper. During test mode, the transient response of the OA under test shall be measured in order to detect any deviation of the overshoot with respect to the fault-free circuit. The overshoot of the transient response is a very sensitive parameter and can be easily obtained by sampling at a particular time. The analog test stimuli signal can be easily generated by means of a current sink made of a single PMOS transistor. The test decision block is purely digital, with only two TDM comparators, two flip-flops and some logical circuitry just to compare fault-free and CUT two-bit signatures. Simulation results show the effectiveness of the proposed technique with low area overhead.