Automated Self-Test of an Analog Delta-Sigma Modulator

Abstract

This project investigates the feasibility of automating the test of ΔΣ-modulators using circuitcomponents available on 8-bit microcontrollers, and by doing so reducing test costs.A Built-In-Self-Test (BIST) scheme, using a binary stream as stimuli and two differentsolutions for signal analysis is suggested and simulated in SPICE to investigate its suitability.The test can not lead to a large area increase, increasing area leads to an increase inproduction cost. The test has to reduce testing time. The extra area occupied by the testarchitecture has to be paid in shorter testing time and therefore a lower unit price. The test hasto remove or lower the requirements of the off-chip tester, and by doing so reducing cost.The proposed BIST requires a very small area and is capable of calculating offset, gain andSignal to Noise Ratio with a high degree of accuracy. The proposed solution enables on-chiptesting without the need for expensive external stimuli and signal analyzers, making testing onwafer possible thus improving production yield.The proposed test will not reduce test time by itself, however by integrating the test on-chipand allowing this to run in the background while other on-chip modules are tested total testtime can be reduced to the time required to shift the stimuli into the chip.