PCA148X datasheet(5/20 Pages) PHILIPS

5 / 20 page

1998 Apr 21

Philips Semiconductors

Product speciﬁcation

32 kHz watch circuits with adaptive motor

pulse

PCA148x series

Voltage level detector

The supply voltage is compared with the internal voltage

reference VEOL every minute. The first voltage level

detection is carried out 30 ms after RESET.

When the detected VDD voltage level is greater than VEOL,

the circuit operates in normal mode (Fig.3).

If the battery end-of-life is detected (VDD < VEOL), the

detection and stage control is switched OFF and the

waveform of stage 6 will be executed. To indicate this

condition the waveform is produced in bursts of 4 pulses

every 4 s.

Detection of motor movement

After a motor pulse, the motor is short-circuited to VDD for

1 ms. Afterwards the energy in the motor inductor will be

dissipated to measure only the current generated by the

induced motor voltage. During the time tDI (dissipation of

energy time) all switches shown in Fig.4 are open to

reduce the current as fast as possible. The current will now

flow through the diodes D3 and D2, or D4 and D1. Then

the first of 52 possible measurement cycles (tMC) starts to

measure the induced current.

Fig.4 Motor driving and detecting circuit.

MSA941

VDD

VSS

MOTOR

PCA148X Datasheet(PDF) 5 Page - NXP Semiconductors