GB1402221A - Electronic watch having quartz crystal controlled oscillator and frequency divider arrangement for driving a display device - Google Patents

Abstract

1402221 Electronic timepieces HUGHES AIRCRAFT CO 13 June 1973 [3 July 1972] 28126/73 Heading G3R [Also in Division H3] In an electronic timepiece (e.g. a ladies watch) comprising a quartz crystal controlled oscillator circuit (providing a time base frequency of at least 1 MHz) and frequency dividing arrangement for driving a time display device (e.g. liquid crystal, light-emitting diodes or an electric motor driving hands), the quartz crystal 13 Fig. 3 is coupled to a first integrated circuit chip 15 including the oscillator circuit and a first frequency divider for dividing down e.g. to about 100 KHz. A second integrated circuit chip 17 is connected to the first and includes a second frequency divider for producing low frequency signals e.g. 1 pulse/hour for driving the display; the second IC chip having an inherently lower leakage current and inherently higher nodal capacitance than the first IC chip. The first IC chip 15, has relatively low nodal capacitance, achieved by the use of a semiconductor layer (silicon) deposited on an insulating layer (sapphire) whereby it can operate at extremely high frequencies without excessive power consumption. The chip 17 also includes electronic circuitry (not described) which produces from the second divider output, signals suitable for driving a digital display as shown Fig. 8. Therein hours, minutes, day and date are displayed, also the first digit of the seconds and ten dots which are illuminated successively to indicate passing seconds. When for instance the 59th second arrives, the first digit "5" and nine dots are illuminated. Battery voltage is converted to a higher voltage to operate a liquid crystal display. Alternatively, the output of the second frequency divider may be used to drive a motor coupled to hands Fig. 11 (not shown). For frequencies in the order of 1MHz, a D.T. cut crystal is used mounted as illustrated in Figs. 4, 5 (not shown). For frequencies about 9 MHz and A.T. cut crystal is used supported at each end, as illustrated Figs. 6, 7 (not shown). Known types of oscillator and frequency divider circuitry employing C/MOS elements may be used. Suitable circuits are illustrated in Figs. 15, 16 (not shown).