MICROCOMPUTER-COMPENNSATED CRYSTAL OSCILLATOR FOR LOW-POWER CLOCKS

S.S. Schodowski, R.L. Filler, J.A. Messina, V.J. Rosati, J.R. Vig

Abstract: Temperature-compensated crystal oscillators (TCXO) are widely used in applications requiring precision frequency control or timing, especially when power availability is limited and the temperature range is wide. The best overall accuracy in wide temperature range (e.g., -55°C to +85°C) TCXo has remained at about 1 ppm for the past 30 years because of thermal hysteresis, the trim effect, and thermometry inaccuracies. In this paper a microcomputer compensated crystal oscillator (MCXo) is described. This MCxo employs external compensation, i.e., there is tuo frequency "pulling". It thrus permits the use of a low-hysteresis, low deviation-sensitivity SCeut crystal in a non-trimmed oscillator. Resonator self-termperature-sensing, using a dual-mode oscillator, virtually eliminates thermometry-related errors. As a consequence, all basic TCxo limitations are overcome or significantly reduced. The MCxo incorporating this technology is capable of providing at least 10- to 100-times improvement in overall frequency accuracy when compared to conventional Texo. Milliseconds-per day timekeeping accuracy, with an input power of less than 40 milliwatts, is now available.
Published in: Proceedings of the 21th Annual Precise Time and Time Interval Systems and Applications Meeting
November 28 - 30, 1989
Sheraton Hotel
Redondo Beach, California
Pages: 445 - 466
Cite this article: Schodowski, S.S., Filler, R.L., Messina, J.A., Rosati, V.J., Vig, J.R., "MICROCOMPUTER-COMPENNSATED CRYSTAL OSCILLATOR FOR LOW-POWER CLOCKS," Proceedings of the 21th Annual Precise Time and Time Interval Systems and Applications Meeting, Redondo Beach, California, November 1989, pp. 445-466.
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