The PCA2003 is a CMOS integrated circuit for battery operated wrist watches with a
32 kHz quartz crystal as timing element and a bipolar 1 Hz stepping motor. The quartz
crystal oscillator and the frequency divider are optimized for minimum power
consumption. A timing accuracy of 1 ppm is achieved with a programmable, digital
To obtain the minimum overall power consumption for the watch, an automatic motor
pulse adaptation function is provided. The circuit supplies only the minimum drive current,
which is necessary to ensure a correct motor step. Changing the drive current of the
motor is achieved by chopping the motor pulse with a variable duty cycle. The pulse
period and the range of the variable duty cycle can be programmed to suit different types
of motors. The automatic pulse adaptation scheme is based on a safe dynamic detection
of successful motor steps.
A pad RESET is provided (used for stopping the motor) for accurate time setting and for
accelerated testing of the watch.