PTAT sensor for chip overheat protection

This paper presents a novel application of a Proportional-To-Absolute-Temperature (PTAT) sensor. The main function of this sensor is to monitor circuit temperature and generate an overheat signal in order to warn about excessive temperature of a circuit. Special emphasis is laid on the description of the design of current mirrors, which are responsible for the output signal voltage drop when circuit temperature exceeds certain preset value. The entire design was validated by measurements of the test ASIC implementing the sensor. The measurements confirmed correct operation of the sensor, but at the same time they revealed high sensitivity of the design to the parameter spread among particular ASICs and to the interference from digital circuitry.