A Subthreshold-MOSFETs-Based Scattered Relative Temperature Sensor Front-End With a Non-Calibrated $\pm 2.5^{\circ}{\rm C}$$3\sigma$ Relative Inaccuracy From -$40^{\circ}{\rm C}$ to 100$^{\circ}{\rm C}$

Abstract

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 μm 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-JP-type threshold voltage of around 0.8 V and 0.9 V at room temperature, respectively. The measured 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.