Phase control of triangular stimulus generator for ADC BIST

Coherent sampling is required in ADC testing. Unlike production testing in which fractional frequency is available, only sampling clock of ADC is available for ADC Built-in Self-test (BIST). Triangular stimulus generator controlled by sampling clock of ADC cannot provide enough information because same voltages are sampled in every period. To carry out valid data acquisition, different voltages in different period should be sampled. Instead of generating fractional frequency, a method of introducing delay to every ramp in triangular wave is proposed in this paper. An 8-bit digital to time converter (DTC) is designed to provide needed number of delays. A control scheme is proposed to provide both phase control of triangular stimulus and testing control of BIST. Simulation results show control scheme works well for linearity test and delayed triangular wave provides valid data acquisition for histogram test. Errors in delay affect test results very little.