A subthreshold-MOSFETs-based scattered relative temperature sensor front-end with a non-calibrated ± 2.5° C 3σ relative inaccuracy From-40° C to 100° C

This paper presents a subthreshold MOSFETs-based scattered relative temperature sensor front-end operating at a low supply voltage. Dynamic element matching and dynamic offset cancellation have been implemented to minimize the errors induced by device mismatches. An individual proportional-to-absolute- temperature (PTAT) voltage generator was first implemented to verify the low voltage operation capability and the mismatch-error correction. A low voltage reference circuit has been also designed and tested. A gate-bulk-driven error correction amplifier is proposed in order to minimize the offset error and maintain low voltage operation. The scattered relative temperature sensor front-end was then implemented in AMI 0.5 μ m CMOS process with an array of 5 × 5 sensor nodes across the chip. The minimum supply voltage was measured as 1 V over-40-100° C, with a typical N-/P-type threshold voltage of around 0.8 V and 0.9 V at room temperature, respectively. The measured 3σ relative inaccuracy was less than ± 2.5° C without calibration. To the best of the authors' knowledge, this is the first time that non-calibrated on-chip relative temperature monitoring accuracy is reported. Furthermore, the multi-location thermal monitoring function has been experimentally demonstrated and a 2 °C/mm on-chip temperature gradient was detected.