A low-cost digital frequency testing approach for mixed-signal devices using ΣΔ modulation

This paper presents a digital approach to frequency testing of Analogue and mixed-signal (AMS) circuits. This approach is aimed at facilitating low-cost test techniques for system-on-chip (SoC) devices, rendering the test of mixed-signal cores compatible with the use of a low-cost digital tester. Analogue test signal generation is performed on-chip by low pass filtering a sigma-delta (ΣΔ) encoded bit-stream. Analogue harmonic test response analysis is also performed on-chip using square wave modulation and ΣΔ modulation. Since both analogue signal generation and test response analysis are digitally programmable on-chip, compatibility with a low-cost digital tester is ensured. Optimisation of test signatures is discussed in detail as a trade-off between fault and yield coverage. A 0.18 μm CMOS implementation of this BIST technique is presented, including some experimental results.