A 200mV Operable On-Chip Temperature Sensor for IoT Devices Powered by Energy Harvesters with Ultra-Low Output Voltage

Kimiyoshi Usami, Songxiang Wang, Kaito Nagai, Giovanna Latronico, Paolo Mele

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This paper describes a 24.8 μm2 on-chip CMOS digital temperature sensor core operable on 95 nW at the 200mV supply voltage. The target of this sensor is IoT devices powered by energy harvesters with ultra-low output voltage such as thermoelectric generators. Unlike the conventional ring-oscillator type temperature sensor, the proposed sensor directly monitors the time to store the electrical charge into the capacitance by temperature-dependent leakage current. The result of this 'temperature-to-time' conversion is given to a counter to obtain a digital output. We designed and fabricated the proposed temperature sensor circuit in a 65 nm FDSOI technology. Measured results demonstrated that the proposed temperature sensor successfully operated at 0.2 V - 1.2 V for the temperature range from -20 °C to 80 °C. Excellent linearity in the relationship between the logarithm value of the counter output and the reciprocal of absolute temperature was demonstrated in an analytical model and confirmed in the measured results. This enables us to identify the temperature from the counter output by a 2-point calibration with good accuracy. Since all MOS transistors for the temperature-to-time conversion operate in the subthreshold region (i.e. at the off-state) in 0.2 V, the accuracy is significantly affected by the process variation. In the proposed temperature sensor, by tuning the body-bias voltage to pMOS (V BS,p) and the reference voltage (VREF), the maximum error in the temperature across four fabricated sensors on a chip was reduced to 0.24X. By tuning V BS,p and VREF to the conversion temperature range [-20 °C, 80°C], the error was improved to +5.7 °C/-5.1 °C, while further improved to +1.2 °C/-2.4 °C by tuning them to the temperature range [0 °C, 80°C].

Original languageEnglish
Title of host publicationProceedings of 2023 IEEE International Conference on Internet of Things and Intelligence Systems, IoTaIS 2023
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages65-71
Number of pages7
ISBN (Electronic)9798350319040
DOIs
Publication statusPublished - 2023
Event2023 IEEE International Conference on Internet of Things and Intelligence Systems, IoTaIS 2023 - Hybrid, Bali, Indonesia
Duration: 2023 Nov 282023 Nov 30

Publication series

NameProceedings of 2023 IEEE International Conference on Internet of Things and Intelligence Systems, IoTaIS 2023

Conference

Conference2023 IEEE International Conference on Internet of Things and Intelligence Systems, IoTaIS 2023
Country/TerritoryIndonesia
CityHybrid, Bali
Period23/11/2823/11/30

Keywords

  • accuracy
  • body bias
  • temperature sensor
  • temperature-to-time conversion
  • ultra-low voltage

ASJC Scopus subject areas

  • Artificial Intelligence
  • Computer Networks and Communications
  • Information Systems
  • Computer Science Applications

Fingerprint

Dive into the research topics of 'A 200mV Operable On-Chip Temperature Sensor for IoT Devices Powered by Energy Harvesters with Ultra-Low Output Voltage'. Together they form a unique fingerprint.

Cite this