Low-voltage temperature sensor for micro-power harvesters in silicon-on-sapphire CMOS

A low-voltage temperature sensor designed for MEMS power harvesting systems is fabricated. The core of the sensor is a bandgap voltage reference circuit operating with a supply voltage in the range 1-1.5 V. The prototype was fabricated on a conventional 0.5 μm silicon-on-sapphire (SOS) process. The sensor design consumes 15 μA of current at 1 V. The internal reference voltage is 550 mV. The temperature sensor has a digital square wave output the frequency of which is proportional to temperature. A linear model of the dependency of output frequency with temperature has a conversion factor of 1.6 kHz/°C. The output is also independent of supply voltage in the range 1-1.5 V. Measured results and targeted applications for the proposed circuit are reported.