Analog/digital ASIC design for testability

The author addresses three issues in design for testability (DFT) for mixed analog/digital application-specific integrated circuit (ASIC) chips: controllability, observability, and completeness in testing. These are examined for commonly used analog functions, and the results culminate in an architecture for testable mixed analog and digital circuits. The architecture is designed to solve the problems associated with testing basic circuit configurations for different types of commonly used analog macros. Using the recommended architecture to gain access to control and observation test points in the analog portions of the mixed analog/digital ASIC, a series of analog test tables for several different analog functions have been derived. The analog test procedures are independent of any digital design for testability that might be used in the digital portions of the ASIC. General testing procedures for current analog/digital ASICs are described along with desirable characteristics for testers for this type of circuit