Chapter 5 Simulation and Measurement results
5.2 Chip Design and Measurement results …
5.2.3 Testing Environment
The test signals with different pulse widths were generated by Agilent Logic Analysis System 16902A feeding into the test chip. The test circuit of the proposed TDC sensor was put in a heater called Low Temperature Incubator.
Agilent Logic Analysis System 16902A was also implemented to collect the output codes of the TDC sensor and to synchronize the operations among the measurement equipments and the TDC test board. DC power supply is provided by Agilent DC Supply E3632A.
Fig.32 The testing equipments and the test chip
Fig.33 The Agilent Logic Analysis System 16902A
Fig.34 The Agilent Logic Analysis System 16902A
Fig.35 The Low Temperature Incubator
Fig.36 The test chip
Chapter 6 Conclusion and Future Research
6.1 Conclusion
The CMOS temperature sensor features an extremely small chip area, low-power consumption with good conversion rate of 1k/s and wide operation range. Discarding any bipolar transistor, external resistor and replacing of voltage analog-to-digital converter used in conventional versions with a circulating TDC, the occupied chip area is merely 0.01004mm2, which is less than one-tenth of those of most former versions with no calibration circuit. As shown by the experiment results, the digital output of the sensor is highly linear and no curvature correction or dynamic offset-cancellation is required to reach satisfactory accuracy. The resolution reaches as precise as 0.14°C. The operational temperature range spans as widely as from -50°C to 120°C.These features make the sensor excellent for accurate low-power portable applications with VLSI or SOC integration. Its simple design and low cost grant it to be easily integrated into any CMOS IC chip. In addition, it’s unique and exclusive on the sub-90nm technology node in the present time.
6.2 Future Research
To achieve better performance yet requires careful refining and tuning. The calibration circuit in this work indeed provides much better resolution and perfect linearity but it is still not good enough. In order to achieve perfection
more sophisticated design and calibration must involve in the future work.
However, the perfection comes with a heavy cost of chip area and power consumption. So the future research will focus on the non-calibration-needed and even lower-cost version on-chip smart temperature sensor with more precision and greater linearity. Techniques like curvature calibration and digital set-point programming could be taken into consideration.
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