1.

General description

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

frequency adjustment.

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.

2.

Features

and high immunity to leakage currents

Programmable (OTP) memory

drive according to the required torque

wide range, stored in OTP memory

PCA2003

32 kHz watch circuit with programmable adaptive motor pulse

and pulse period

Rev. 02 — 21 July 2009

Product data sheet