Title :
A microprocessor-based analog wristwatch chip with 3 seconds/year accuracy
Author :
Lanfranchi, D. ; Dijkstra, E. ; Aebischer, D.
Author_Institution :
Swiss Center for Electron. & Microtechnol. Inc., Neuchatel, Switzerland
Abstract :
Previous developments on a 2.1MHz quartz have demonstrated that thermal, ageing and shock performances are improved by at least one order of magnitude compared to a 32kHz quartz. The temperature behavior is a flat cubic function, and therefore positive and negative deviations with respect to the reference temperature are compensated. A field test on 20 watch samples containing an oscillator built around this quartz showed that over a 3-year period, the maximum deviation is less than 3 seconds/year. Note that these results are obtained without any temperature compensation scheme. As the power consumption of a 2.1 MHz quartz oscillator (2.3/spl mu/A) is not compatible with the power consumption of standard watch oscillator circuits (<300nA), the 2.1MHz quartz oscillator is periodically powered for a short time and locks a continuously-running 32MHz, 200nA quartz oscillator. While short term precision is provided by the 32MHz oscillator, longer-term deviations are corrected by the periodically activated 2.1MHz oscillator. The chosen periodicity is 10 minutes, corresponding to the thermal constants in a watch.<>
Keywords :
ageing; clocks; crystal resonators; harmonic oscillators (circuits); quartz; 10 min; 2.1 MHz; 2.3 muA; SiO/sub 2/; ageing; flat cubic function; microprocessor-based analog wristwatch chip; periodicity; power consumption; quartz oscillator; reference temperature; shock performances; temperature behavior; thermal constants; watch oscillator circuits; Aging; Circuit stability; Circuits and systems; Electric shock; Energy consumption; Frequency; Oscillators; Temperature measurement; Temperature sensors; Watches;
Conference_Titel :
Solid-State Circuits Conference, 1994. Digest of Technical Papers. 41st ISSCC., 1994 IEEE International
Conference_Location :
San Francisco, CA, USA
Print_ISBN :
0-7803-1844-7
DOI :
10.1109/ISSCC.1994.344713