A +0.66/−0.73 °C Inaccuracy, 1.99-μW Time-Domain CMOS Temperature Sensor With Second-Order ΔΣ Modulator and On-Chip Reference Clock

This paper presents a compact and low-power time-domain CMOS temperature sensor intended for Internet of Things. To eliminate the off-chip reference clock that is commonly needed for time-domain CMOS temperature sensors, a precise on-chip reference clock is designed to measure the temperature-dependent delay generated by an inverter chain with even stages. In the reference clock circuit, a relaxation oscillator showing discharging phases with negative temperature coefficient (TC) is designed, which are compensated by 2 identical inverter-chains with positive-TC delay, resulting in a reference clock with nearly temperature-independent pulse width and period. In addition, a <inline-formula> <tex-math notation="LaTeX">$2^{{\text {nd}}}$ </tex-math></inline-formula>-order hybrid time-voltage delta-sigma (<inline-formula> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula>) modulator with feedforward path is proposed to quantize the temperature-dependent delay of the main inverter chain, achieving 100-mK resolution only in about 25-ms conversion time. Fabricated in 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS, measurement results show that the best (worst)-case temperature accuracy of the clock’s reference time is ±0.015% (±0.055%) and the temperature sensor achieves a maximum inaccuracy of +0.66/−0.73 °C from −20 °C to −80 °C. The prototype occupies 0.45-mm<sup>2</sup> chip area and consumes 1.99-<inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> from a 1.8-V supply at room temperature.

[1]  Jae-Yoon Sim,et al.  A 2 GHz fractional-N digital PLL with 1b noise shaping ΔΣ TDC , 2011, 2011 Symposium on VLSI Circuits - Digest of Technical Papers.

[2]  David Blaauw,et al.  A Fully-Integrated 71 nW CMOS Temperature Sensor for Low Power Wireless Sensor Nodes , 2014, IEEE Journal of Solid-State Circuits.

[3]  Kofi A. A. Makinwa,et al.  A resistor-based temperature sensor for MEMS frequency references , 2013, 2013 Proceedings of the ESSCIRC (ESSCIRC).

[4]  Kofi A. A. Makinwa,et al.  3.6 A CMOS Resistor-Based Temperature Sensor with a 10fJ·K2 Resolution FoM and 0.4°C (30) Inaccuracy From −55°C to 125°C After a 1-point Trim , 2020, 2020 IEEE International Solid- State Circuits Conference - (ISSCC).

[5]  Kofi Makinwa,et al.  13.1 A CMOS Temperature Sensor with a 3σ Inaccuracy of ±0.1°C from –55°C to 125°C , 2000 .

[6]  David Blaauw,et al.  9.2 A 0.6nJ −0.22/+0.19°C inaccuracy temperature sensor using exponential subthreshold oscillation dependence , 2017, 2017 IEEE International Solid-State Circuits Conference (ISSCC).

[7]  Hui Wang,et al.  A 1.6%/V 124.2 pW 9.3 Hz relaxation oscillator featuring a 49.7 pW voltage and current reference generator , 2017, ESSCIRC 2017 - 43rd IEEE European Solid State Circuits Conference.

[8]  Kamran Souri,et al.  A 0.12mm2 7.4μW micropower temperature sensor with an inaccuracy of ±0.2°C (3σ) from −30°C to 125°C , 2010, 2010 Proceedings of ESSCIRC.

[9]  Kofi A. A. Makinwa,et al.  10.3 A 0.12mm2 Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C , 2019, 2019 IEEE International Solid- State Circuits Conference - (ISSCC).

[10]  Hui Wang,et al.  A 51 pW reference-free capacitive-discharging oscillator architecture operating at 2.8 Hz , 2015, 2015 IEEE Custom Integrated Circuits Conference (CICC).

[11]  Hui Wang,et al.  A Reference-Free Capacitive-Discharging Oscillator Architecture Consuming 44.4 pW/75.6 nW at 2.8 Hz/6.4 kHz , 2016, IEEE Journal of Solid-State Circuits.

[12]  P. Mercier,et al.  Near-Zero-Power Temperature Sensing via Tunneling Currents Through Complementary Metal-Oxide-Semiconductor Transistors , 2017, Scientific Reports.

[13]  Patrick P. Mercier,et al.  A 763 pW 230 pJ/Conversion Fully Integrated CMOS Temperature-to-Digital Converter With +0.81 °C/−0.75 °C Inaccuracy , 2019, IEEE Journal of Solid-State Circuits.

[14]  J. Burm,et al.  An Ultralow Power Time-Domain Temperature Sensor With Time-Domain Delta–Sigma TDC , 2017, IEEE Transactions on Circuits and Systems II: Express Briefs.

[15]  I. Filanovsky,et al.  Mutual compensation of mobility and threshold voltage temperature effects with applications in CMOS circuits , 2001 .

[16]  Yuanjin Zheng,et al.  A new time-mode on-chip oscillator-based low power temperature sensor , 2015, 2015 IEEE International Conference on Electron Devices and Solid-State Circuits (EDSSC).

[17]  David Blaauw,et al.  An ultra low power 1V, 220nW temperature sensor for passive wireless applications , 2008, 2008 IEEE Custom Integrated Circuits Conference.

[18]  Urs Denier,et al.  Analysis and Design of an Ultralow-Power CMOS Relaxation Oscillator , 2010, IEEE Transactions on Circuits and Systems I: Regular Papers.

[19]  A. Cabrini,et al.  A small-size, fast-settling, low-cost thermal regulator for chip surface measurements , 2004, Proceedings of the 21st IEEE Instrumentation and Measurement Technology Conference (IEEE Cat. No.04CH37510).

[20]  Kofi A. A. Makinwa,et al.  A CMOS temperature sensor with a voltage-calibrated inaccuracy of ±0.15°C (3σ) from −55 to 125°C , 2012, 2012 IEEE International Solid-State Circuits Conference.

[21]  Yuan Cao,et al.  A 0.6V 75nW All-CMOS Temperature Sensor With 1.67m°C/mV Supply Sensitivity , 2017, IEEE Transactions on Circuits and Systems I: Regular Papers.

[22]  Johan H. Huijsing,et al.  Precision Temperature Sensors in CMOS Technology , 2006 .

[23]  Kofi A. A. Makinwa,et al.  A CMOS temperature sensor with a voltage-calibrated inaccuracy of ±0.15°C (3σ) from −55 to 125°C , 2012, 2012 IEEE International Solid-State Circuits Conference.

[24]  Poki Chen,et al.  A Time-Domain SAR Smart Temperature Sensor With Curvature Compensation and a 3σ Inaccuracy of −0.4°C ∼ +0.6°C Over a 0°C to 90°C Range , 2010, IEEE Journal of Solid-State Circuits.

[25]  Arun Paidimarri,et al.  A 120nW 18.5kHz RC oscillator with comparator offset cancellation for ±0.25% temperature stability , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[26]  Seok-Kyun Han,et al.  A low power low inaccuracy linearity-compensated temperature sensor for attachable medical devices , 2013, 2013 IEEE International Symposium on Circuits and Systems (ISCAS2013).

[27]  Takayasu Sakurai,et al.  An 11-nW CMOS Temperature-to-Digital Converter Utilizing Sub-Threshold Current at Sub-Thermal Drain Voltage , 2019, IEEE Journal of Solid-State Circuits.

[28]  Kofi A. A. Makinwa,et al.  A 0.12 mm 2 7.4 μ W Micropower Temperature Sensor With an Inaccuracy of ± 0.2°C (3 Sigma ) From - 30°C to 125°C , 2011, IEEE J. Solid State Circuits.