A 1-V 15 µ W high-precision temperature switch

A CMOS temperature switch with uncalibrated high temperature accuracy is presented. The circuit is based on the classical CMOS bandgap reference structure, using parasitic PNPs and a PTAT multiplier. The circuit was designed in a standard digital 0.18 µm CMOS process. The temperature switch has a in-designed hysteresis of 1.2° C around a threshold value of 128° C. At the switching-threshold all matched transistors have also matched operating conditions, yielding a temperature threshold that is highly independent of transistor output resistance and supply voltage. With a chip area of only 0.03 mm²:, the on-wafer 3σ spread of the threshold temperature is 1.1° C. Power consumption is only 15 µA at 1 Volt supply.