A general theory for accurately analyzing the nonlinear behaviour of any crystal oscillator circuit is presented. The conditions for growing and for stable oscillation are given and the effects of nonlinearities are discussed. The special case of the three-point oscillator is analyzed in more detail. The basic conditions and trade-offs are derived analytically for the case of a lossless circuit, and current minimization by amplitude regulation is explained. As an application, a 2.1 MHz CMOS oscillator is described, which uses amplitude regulation and direct coupling of the oscillator core to the first divider to minimize power consumption. The chip, implemented in a 2 μm n-well process, includes a frequency-divider chain and the front-end for digital tuning. It operates from 1.8 to 3.5 volts with less than 500 nA. The measured frequency stability is 0.04 ppm/V and 0.1ppm/°C.
KeywordsActive Device Stable Oscillation Input Capacitance Crystal Oscillator Weak Inversion
Unable to display preview. Download preview PDF.
- E. Vittoz, “Large-scale integration in watches”, ESSCIRC76, Solid-State Circuits 1976, Ed. Journal de Physique, 1977, Paris. Also published in Pulse, pp.l4–20, Jan.l978.Google Scholar
- L. Astier, CSEM internal report.Google Scholar
- E. Vittoz, “Micropower techniques”, in Design for VLSI Circuits for Telecommunication and Signal Processing, Editors J. Franca and Y. Tsividis, Prentice Hall, 1994.Google Scholar
- J. Hermann, “A novel miniature ZT-cut quartz”, Proc. 39th Frequency Symposium, pp. 375–380, 1986.Google Scholar
- R. Iwakura et al., “Low-Power IC for 4.2MHz Analog Wrist Watch”, Societé Suisse de Chronométrie, October 1981.Google Scholar
- J. Lüscher and A. Rusznyak, “A 4.2MHz Quartz Oscillator for Watch Applications”, Bull. ASE/UCS 73, Feb, 1982.Google Scholar
- D. Lanfranchi et al. “A Microprocessor-Based Analog Wristwatch Chip with 3 Seconds/Year Accuracy”, ISSCC94, WP 5.6., February pp.16–18, 1994, San Francisco, CAGoogle Scholar
- E.A. Vittoz, H. Oguey, “Complementary Dynamic MOS Logic Circuits”, Electronics Letters, Vol 9, N°4, 22nd February 1973.Google Scholar