Delta-Sigma Based CMOS Stress Sensor with RF Output

A CMOS stress sensor is merged with a delta-sigma modulator to produce a sensor with a low frequency RF output. A PMOS current mirror with two orthogonal transistors is used as the stress sensor. The delta-sigma modulator generates an output signal that can be processed digitally or monitored by a communications receiver. The frequency shift of the DSBSC output of the modulator is directly proportional to the stress induced mismatch in the sensor cell. A test chip demonstrating the sensor has been fabricated using the 1.5 mum MOSIS CMOS process.