32 KHz Watch Circuit with Programmable Output Period and Pulse Width

PCA2002

The PCA2002 is a CMOS integrated circuit for battery operated wrist watches with a 32 kHz quartz crystal as the timing element and a bipolar stepping motor. The quartz crystal oscillator and the frequency divider are optimized for minimum current consumption. A timing accuracy of 1 ppm is achieved with a programmable, digital frequency adjustment.

The output period and the output pulse width can be programmed. It can be selected between a full output pulse or a chopped output pulse with a duty cycle of 75 %. In addition, a stretching pulse can be added to the primary driving pulse.

A pad RESET is provided (used for stopping the motor) for accurate time setting and for accelerated testing of the watch.

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PCA2002 Block Diagram

PCA2002 Block Diagram

Block diagram: PCA2002CX8, PCA2002U, PCA2003U

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Features

  • Amplitude-regulated 32 kHz quartz crystal oscillator, with excellent frequency stability and high immunity to leakage currents
  • Electrically programmable time calibration with 1 ppm resolution stored in One Time Programmable (OTP) memory
  • The quartz crystal is the only external component required
  • Very low current consumption: typically 90 nA
  • Output pulses for bipolar stepping motors
  • Five different programmable output periods (1 s to 30 s)
  • Output pulse width programmable between 1 ms and 8 ms
  • Full or chopped motor pulse and pulse stretching, selectable
  • Stop function for accurate time setting and current saving during shelf life
  • Test mode for accelerated testing of the mechanical parts of the watch
  • Test bits for type recognition

Target Applications

  • Driver circuits for bipolar stepping motors
  • High immunity motor drive circuits
  • High production volumes

部品番号： PCA2002U, PCA2002DUS.

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