Design Files
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32 KHz Watch Circuit with Programmable Output Period and Pulse Width
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.
Product Details
Block Diagram
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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
Part numbers include: PCA2002DUS, PCA2002U.
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Documentation
Quick reference to our documentation types.
4 documents
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Application Note
Programming the PCA200x family of watch ICs
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Application Note
ESD and EMC sensitivity of IC
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Application Note
Handling bare die
Design Resources
Engineering Services
To get further assistance directly from NXP, please see our Engineering Services.
1 engineering service
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Independent Design House (IDH)
Embedded Software Design
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