Testing digital/analog and analog/digital converters

This paper describes several D/A and A/D converter test circuits which range from simple and low-cost to fully automatic and expensive. Methods are presented to measure the more important specifications of offset, gain, full scale, linearity, and differential linearity errors. The discussions focus on, but are not limited to, testing 12-bit converters. Guidelines are given for determining the required accuracy of the measurement standard and for using proper circuit layout and wiring. Part of the test circuits are static and use a DVM as a reference. Other testers are dynamic and use a fast-settling D/A converter as a reference. Many of the circuits are manually operated, but others are automated using a computing controller. The unique characteristics of converters such as the symmetrical error patterns and the dynamic errors are discussed in light of how they relate to the techniques chosen to measure the errors. Part of the test methods assume that the weight of each bit in a converter is completely independent of the on/off state of the other bits (low superposition errors). When superposition errors are not small, they must be considered before choosing a test method. In general, the intent of this paper is to lay enough ground work so that the user of converter products can implement a test system that is both economical and sufficient to produce the desired results.