Strategies and structures for test access in mixed-signal MCMs

This paper describes a framework of strategies and structures to provide test access to mixed analog-digital MCMs. Recognizing that these mixed-signal devices contain a wide variety of components (from passive to active, from ASICs to off-the-shelf parts), the strategies presented include hierarchies of test access, and circuits to implement them. Frequently used structures such as the classical multiplexers and IEEE Std. 1149.1 are integrated with new structures more suitable for analog and mixed-signal test, such as current-based analog scan and IEEE P1149.4. Five general access circuit types and four major control topologies are described taking into account the requirements for test accuracy and the tradeoffs involved in design and test.