Oscillation prevention during testing of integrated circuit logic chips

Abstract

Integrated circuit logic chips often oscillate during testing because the large unbypassed inductance of the test fixture causes off-chip driver switching noise to be fed back to the logic chip power supply. Oscillation may be prevented by adding an inhibit receiver and an off-chip driver inhibit network to the logic chip. The off-chip driver inhibit network provides a fan out path from the inhibit receiver to each off-chip driver. In response to an inhibit signal applied to the inhibit receiver, the inhibit network forces each of the off-chip drivers to the same logical state, the logic state being the natural logic state assumed by the off-chip drivers upon initial application of power to the chip. The driver inhibit receiver and inhibit network are employed to prevent oscillation at chip power-on, during driver and receiver parametric testing and during input test pattern tests.