Using Optimized Butterworth-Based $\Sigma\Delta$ Bitstreams for the Testing of High-Resolution Data Converters

Testing high-resolution data converters is often performed using Automatic Test Equipment (ATE) that has lower resolution Integrated Chips (ICs). Hence, indirect voltage measurements are required. To perform these measurements programmable DC voltage sources are essential. An area efficient technique in generating DC voltage sources is the one that saves a ΣΔ bitstream generated in software in the memory of an ATE and apply it periodically to a low-pass filter (LPF). The Noise Transfer Function (NTF) of the ΣΔM has been selected from the Butterworth, Butterworth with zeros, Bessel and Gaussian families for ΣΔM orders from 1 to 4. An investigation was conducted to figure out the best ΣΔM type and order that should be used. It will be shown that using a high-order Butterworth-based ΣΔ bitstream yields the lowest settling time. This means the DC voltage levels will be available for usage quicker than the other ΣΔM types. Hence, reducing the time taken to test an IC, which in-turn minimizes the time to market and maximizes profit margins.