An embedded offset and gain instrument for OpAmp IPs

Abstract

Analog and mixed-signal IPs are increasingly required to use digital fabrication technologies and are deeply embedded into system-on-chips (SoC). These developments append more requirements and challenges on analog testing methodologies. Traditional analog testing methods suffer from less accessibility and control with regard to these embedded analog circuits in SoCs. As an alternative, an embedded instrument for analog OpAmp IP tests is proposed in this paper. It can provide the exact gain and offset values of OpAmps instead of only pass/fail result. What's more, it is an non-invasive monitor and can work online without isolating the DUT Opamp from its surrounding feedback networks. Nor does it require accurate test stimulations. In addition, the monitor can remove its own offsets without additional complex self-calibration circuits. All self-calibrations are completed in the digital domain after each measurement in real time. Therefore it is also suitable for aging-sensitive applications, in which the monitor may suffer from aging mechanisms and has additional offset drifts as well. The monitor measurement range for offset is from 0.2mV to 70mV, and for gain it is from 0dB to 40dB. The error for offset measurements can be 10% of the measurement value with plus/minus 0.1mV, and -2.5dB for gain measurements.