A Dual Mode All NMOS 7-T Temperature Sensor and Voltage Reference for Biomedical Applications

Abstract

This work presents a versatile all-NMOS circuit with dual functions, i.e. either as a conventional temperature sensor or as a precise voltage reference, meeting the vital demand for multi-functional, reusable circuits, thus reducing chip area and power consumption constraints. The circuit can measure temperature in one mode and guarantee the reliable function of implants/wearables by delivering a temperature invariant stable reference voltage in the other mode. The circuit works for a wide temperature range of -40°C to 80°C, without needing extra circuits such as operational amplifiers, startup circuits, or resistors. Implemented in a 65 nm bulk CMOS technology, the circuit occupies an area of 0.00393 mm2. The mode of operation can be controlled by a mode control bit. In voltage reference mode, the circuit has a low temperature coefficient of 96 ppm/°C with an output voltage of 604.3 mV at room temperature. The line sensitivity of the circuit is 0.397 %/V in the operation range of 0.7 V to 1.2 V, consuming a power of 21.23 nW. In the temperature sensing mode, the circuit consumes a power of 42.75 nW, with a temperature inaccuracy of +0.929°C/-1.42°C.