An Ultralow Power Time-Domain Temperature Sensor With Time-Domain Delta–Sigma TDC
- 25 November 2015
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Circuits and Systems II: Express Briefs
- Vol. 64 (10), 1117-1121
- https://doi.org/10.1109/tcsii.2015.2503717
Abstract
Without using bipolar transistors, serially connected inverter cells generate clock delay according to temperature. The delay is compared with a reference clock to estimate the temperature. The proposed time-to-digital converter (TDC) structure is using a time-domain delta–sigma $(\Delta\Sigma)$ modulator. This type of TDC with $\Delta\Sigma$ modulator can achieve higher resolution by increasing the oversampling ratio, with the advantages of low area and low power consumption. To increase the accuracy by producing true temperature-independent time delay, an external reference clock is utilized, instead of temperature-independent inverter cells, for robust operations. The measured temperature sensors demonstrated a minimum power consumption of 480 nW and a resolution under 0.1 °C. The $3\sigma$ error of the sensor is ±0.99 °C over −20 °C–80 °C temperature range from ten-sample measurement results. The chip area is 0.089 mm2 using a Dongbu 0.18-$\mu\mbox{m}$ CMOS process. The conversion rate is 1.25 samples/s.
Keywords
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