A CMOS circuit for real-time chip temperature measurement

The usual way to measure chip temperature is to measure the forward voltage, V/sub f/, of the temperature-characterized on-chip diode. Unfortunately, the diode V/sub f/ measurement is obscured by switching noise on the chip if the chip is running. The noise makes it impractical, if not impossible, to measure the V/sub f/ and temperature of a chip during actual operation. A noise-immune chip temperature sensor circuit has been designed and implemented on Intergraph Clipper C400 CMOS chips. The temperature sensor is a current-controlled CMOS ring oscillator which sends out a squarewave signal whose frequency decreases with temperature. The sensor and signal are relatively immune to the noise of the CMOS chip. The noise immunity allows the chip temperature to be measured while the chip is running. This paper describes the design, performance, and some applications of this real-time chip temperature measuring circuit.<>