1. General description
The PCA2002 is a CMOS
1
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.
2. Features and benefits
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
3. Applications
Driver circuits for bipolar stepping motors
High immunity motor drive circuits
High production volumes
PCA2002
32 kHz watch circuit with programmable output period and
pulse width
Rev. 8 — 25 November 2011 Product data sheet
1. The definition of the abbreviations and acronyms used in this data sheet can be found in Section 15.
