A 840μm2 557nW all-MOS temperature sensor front-end for SoC thermal monitoring

This letter presents an 840μm2 557nW temperature sensor front-end designed for SoC thermal monitoring. The circuit is implemented using MOS transistors exclusively, which enhances its scalability with process technologies and compatibility with digital circuit processes. To address MOSFETs circuit’s process variation issues, a differential voltage readout scheme is employed. Dynamic element matching is used to minimize mismatch of the circuit. The sensor is self-referenced, eliminating the need for an external reference voltage. It is prototyped in a 55nm technology, and the measurement results showed an error of -3.9/3.4°C across 40 samples over a temperature range of 0°C to 90°C without calibration. After a low-cost one-point calibration at room temperature, the error was further reduced to -1.4/1.8°C.