The PCF2003 is a CMOS integrated circuit for battery operated wrist watches with a 32 kHzquartz crystal as timing element and a bipolar 1 Hz stepping motor. The quartz crystaloscillator and the frequency divider are optimized for minimum power consumption. Atiming accuracy of 1 ppm is achieved with a programmable, digital frequencyadjustment.

To obtain the minimum overall power consumption for the watch, an automatic motor pulseadaptation 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 themotor is achieved by chopping the motor pulse with a variable duty cycle. The pulseperiod and the range of the variable duty cycle can be programmed to suit differenttypes of motors. The automatic pulse adaptation scheme is based on a safe dynamicdetection of successful motor steps.

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

• Amplitude-regulated 32 kHz quartz crystal oscillator, with excellent frequencystability and high immunity to leakage currents
• Electrically programmable time calibration with 1 ppm resolution stored in OneTime Programmable (OTP) memory
• The quartz crystal is the only external component connected
• Very low supply current, typical 90 nA
• One second output pulses for bipolar stepping motor
• Five different programmable output periods (1 s to 30 s)
• Minimum power consumption for the entire watch, due to self adaptation of themotor drive according to the required torque
• Reliable step detection circuit
• Motor pulse width, pulse modulation, and pulse adaptation range programmable in awide range, stored in OTP memory
• Stop function for accurate time setting and power saving during shelf life
• Test mode for accelerated testing of the mechanical parts of the watch and theIC
• Test bits for type recognition

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