This document describes the features and characteristics of the PCA146x series 32 kHz watch circuits, including frequency stability, high immunity of the oscillator to leakage currents, time calibration that is electrically programmable and reprogrammable via EEPROM, low current consumption with only a quartz crystal as the external component, output for different types of bipolar stepping motors, up to 50% reduction in motor current compared to conventional circuits by adapting the motor pulse width to match the required torque, on-chip detection of induced motor voltage to prevent loss of motor steps, detector for lithium or silver-oxide battery voltage levels, indication for battery end-of-life, stop function for accurate timing, power-on reset for fast testing, and various test modes for testing the mechanical parts of the watch and the IC.
The PCA146x series devices are CMOS integrated circuits specially suited for battery-operated, quartz-crystal-controlled wrist-watches with a bipolar stepping motor. The circuit includes a 32 kHz oscillator regulated by amplitude to ensure excellent frequency stability.
A key feature is the adaptive motor pulse function, which reduces motor current consumption by up to 50% compared to conventional circuits. It achieves this by self-adapting the motor pulse width to match the required torque of the specific motor used.
A quartz crystal is the only external component required for operation.
The waveform is produced in bursts of 4 pulses every 4 seconds to indicate this condition.
The circuit goes into stage 2 and repeats the sequence through to stage 8.