PCA146X datasheet(3/24 Pages) PHILIPS

3 / 24 page

1998 Apr 21

Philips Semiconductors

Product speciﬁcation

32 kHz watch circuits with adaptive motor

pulse

PCA146x series

PINNING

SYMBOL

DESCRIPTION

VSS

ground (0 V)

TEST

test output

OSC IN

oscillator input

OSC OUT

oscillator output

VDD

supply voltage

motor 1 output

motor 2 output

RESET

reset input

Fig.1 Pin configuration, PCA146xT, (PMFP8).

PCA146xT

VSS

TEST

OSC IN

OSC OUT

RESET

VDD

MSA937

FUNCTIONAL DESCRIPTION AND TESTING

The motor output delivers pulses of six different stages

depending on the torque required to turn the motor

(Figs. 3 and 4). Every motor pulse is followed by a

detection phase which monitors the waveform of the

induced motor voltage. When a step is missed a correction

sequence will be started (Fig.2).

Motor pulses

The circuit produces motor pulses of six different stages

(stage 1 to 5, stage 8). Each stage has two independent

modes: silver-oxide and lithium. The voltage level of VDD

determines which mode is selected (see Section “Voltage

level detector”).

Stages 1 to 5 (both modes) are used in normal operation,

stage 8 occurs under the following conditions:

• Correction pulse after a missing step (both modes)

• End-of-life mode

• If stage 5 is not enough to turn the motor (both modes).

In the silver-oxide mode, the ON state of the motor pulse

varies between 56.25% and 100% of the duty factor

tDF = 977 µs depending on the stage (Fig.3). It increases

in steps of 6.25% per stage.

In the lithium mode, the ON state of the motor pulse is

reduced by 18.75% of the duty factor tDF (Fig.4) to

compensate for the increase in the voltage level.

After a RESET the circuit always starts and continues with

stage 1, when all motor pulses have been executed.

A failure to execute all motor pulses results in the circuit

going into stage 2, this sequence will be repeated through

to stage 8.

When the motor pulses at stage 5 are not large enough to

turn the motor, stage 8 is implemented for a maximum of

8 minutes with no attempt to keep current consumption

low. After stage 8 has been executed the procedure is

repeated from RESET.

The circuit operates for 8 minutes at a fixed stage, if every

motor pulse is executed. The next 480 motor pulses are

then produced at the next lower stage unless a missing

step is detected. If a step is missed a correction sequence

is produced and for a maximum of 8 minutes the motor

pulses are increased by one stage.

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