Built-in self test technique for programmable impedance drivers for RapidChip and ASIC drivers

摘要

A circuit which includes the addition of test points and analog circuitry required to perform a four-point measurement technique. Test points are fed to an analog multiplexer which is under control of test logic added to the design to facilitate the testing. The output of the analog multiplexer is fed directly to an n-bit Analog-to-Digital Converter (ADC), when the number of bits is determined by the measurement resolution required for the circuit to be tested. The ADC is controlled by digital test logic instantiated in the design to perform the BIST operation. A known current is injected and held constant during the entire BIST operation, and the BIST logic performs voltage measurements. The voltage differential is compared by the BIST circuitry based on the values obtained from the ADC. Then, a pass/fail bit can be passed to a signal pin on the device to be compared by the ATE.