Browsing by Author "Peng, Hsuan-Wen"

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A Low-ppm Digitally Controlled Crystal Oscillator Compensated by a New 0.19-mm(2) Time-Domain Temperature Sensor
(2017-01-01)
Tran, Trong-Hieu
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Peng, Hsuan-Wen
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Chao, Paul C. -P.
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Hsieh, Jing-Wen
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電子工程學系及電子研究所
A low-ppm digitally controlled crystal oscillator (DCXO) in a Pierce readout topology with a new 0.19-mm(2) CMOS time-domain temperature sensor (TDTS) circuit for temperature compensation is designed and fabricated in this paper. The Pierce readout circuit is designed to output a 16-MHz oscillating signal as an important base clock for mobile devices. To cope with inevitable imprecision caused by environmental temperature variation, the readout should be compensated based on crystal\'s frequency-temperature curve via a temperature sensor. To this end, a new low-power, small-sized, CMOS on-chip temperature sensor circuit is successfully synthesized by 20-stages of newly designed delay cells. Each delay cell is compensated by a CMOS-process-compatible varactor, enabling a TDTS consisting of only a low number of delay cells to generate long enough delay that is proportional to temperature and in required precisions. In addition to Pierce and TDTS circuits, the DCXO consists of the logics to compute capacitance correction, a switched-capacitor array to adjust Pierce capacitances, and regulators for DCXO and TDTS. The proposed circuits are fabricated by TSMC 0.18-mu m CMOS process, where the active area is 0.516 mm(2) for the whole chip, while 0.19 mm(2) for the TDTS. With temperature compensation enabled, the best measured frequency deviations of a calibrated TCXO is within +/- 0.2 ppm from -40 degrees C to 85 degrees C. The temperature resolution of the developed TDTS is successfully designed to reach 0.18 degrees C/LSB with an accuracy of +/- 1 degrees C validated by one of the tape-out chips.
A New Small-Sized Pierce Crystal Oscillator Readout with Novel on-Chip All-Digital Temperature Sensing and Compensation
(2014)
Peng, Hsuan-Wen
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Su, Chung-Hsin
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Chao, Paul C. -P.
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Hsieh, Jing-Wen
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Chang, Chun-Kai
This paper presents a 16-MHz digital-controlled crystal oscillator and a time-domain temperature sensor design to achieve a high precision temperature-compensated crystal oscillator in a low-power mobile device. The digital-controlled crystal oscillator is based on Pierce topology with two 8-bit switched-capacitor arrays and the temperature of it is measured by time-domain temperature sensor. For noise reduction, the supply voltages of digital-controlled crystal oscillator and time-domain temperature sensor are regulated at 1.2 V by using two on-chip low-dropout regulators. The proposed circuit design has been successfully fabricated by using TSMC 0.18-mu m CMOS process, where the active area is 0.516 mm(2). The measured start-up time of fabricated 8-bit digital-controlled crystal oscillator is about 0.35 ms and the measured phase noise of 1 kHz offset at 25 degrees C is -119.93 dB/Hz. With temperature compensation, the frequency deviation of it is within +/- 0.08 ppm over -40 degrees C to 85 degrees C. The measured effective temperature resolution of time-domain temperature sensor is 0.45 degrees C/LSB and the measured error is within -6.3 degrees C to 7.1 degrees C at 10 Hz conversion rate. The measured current consumption of chip is about 2 mA.