Design for testability of embedded integrated operationalamplifiers

摘要

The operational amplifier (op amp) is one of the most encounterednanalog building blocks. In this paper, the problem of testing annintegrated op amp is treated. A new low-cost vectorless test solution,nknown as oscillation test, is investigated to test the op amp. Duringnthe test mode, the op amps are converted to a circuit that oscillatesnand the oscillation frequency is evaluated to monitor faults. Thentolerance band of the oscillation frequency is determined using a MontenCarlo analysis taking into account the nominal tolerance of allnimportant technology and design parameters. Faults in the op amps underntest which cause the oscillation frequency to exit the tolerance bandncan therefore be detected. Some Design for Testability (DfT) rules tonrearrange op amps to form oscillators are presented and the relatednpractical problems and limitations are discussed. The oscillationnfrequency can be easily and precisely evaluated using pure digitalncircuitry. The simulation and practical implementation results confirmnthat the presented techniques ensure a high fault coverage with a lownarea overhead