I/sub DDQ? test using built-in current sensing of supply line voltage drop

Abstract

A practical built-in current sensor (BICS) is described that senses the voltage drop on supply lines caused by quiescent current leakage. This non-invasive procedure avoids any performance degradation. The sensor performs analog-to-digital conversion of the input signal using a stochastic process, with scan chain readout. Self-calibration and digital chopping are used to minimize offset and low frequency noise and drift. The measurement results of a 350 nm test chip are described. The sensor achieves a resolution of 182 µA, with the promise of much higher resolution.