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A Linearity-Enhanced Time-Domain CMOS Thermostat with Process-Variation Calibration
- Source :
- Sensors, Vol 14, Iss 10, Pp 18784-18799 (2014)
- Publication Year :
- 2014
- Publisher :
- MDPI AG, 2014.
-
Abstract
- This study proposes a linearity-enhanced time-domain complementary metal-oxide semiconductor (CMOS) thermostat with process-variation calibration for improving the accuracy, expanding the operating temperature range, and reducing test costs. For sensing temperatures in the time domain, the large characteristic curve of a CMOS inverter markedly affects the accuracy, particularly when the operating temperature range is increased. To enhance the on-chip linearity, this study proposes a novel temperature-sensing cell comprising a simple buffer and a buffer with a thermal-compensation circuit to achieve a linearised delay. Thus, a linearity-enhanced oscillator consisting of these cells can generate an oscillation period with high linearity. To achieve one-point calibration support, an adjustable-gain time stretcher and calibration circuit were adopted for the process-variation calibration. The programmable temperature set point was determined using a reference clock and a second (identical) adjustable-gain time stretcher. A delay-time comparator with a built-in customised hysteresis circuit was used to perform a time comparison to obtain an appropriate response. Based on the proposed design, a thermostat with a small area of 0.067 mm2 was fabricated using a TSMC 0.35-μm 2P4M CMOS process, and a robust resolution of 0.05 °C and dissipation of 25 μW were achieved at a sample rate of 10 samples/s. An inaccuracy of −0.35 °C to 1.35 °C was achieved after one-point calibration at temperatures ranging from −40 °C to 120 °C. Compared with existing thermostats, the proposed thermostat substantially improves the circuit area, accuracy, operating temperature range, and test costs.
- Subjects :
- thermostat
CMOS
time-domain
linearity enhancement
Chemical technology
TP1-1185
Subjects
Details
- Language :
- English
- ISSN :
- 14248220
- Volume :
- 14
- Issue :
- 10
- Database :
- Directory of Open Access Journals
- Journal :
- Sensors
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.60b52a4fbc0b43a5a4f0f493632b383d
- Document Type :
- article
- Full Text :
- https://doi.org/10.3390/s141018784