PCA2000 datasheet(12/19 Pages) PHILIPS

12 / 19 page

2003 Dec 17

Philips Semiconductors

Product speciﬁcation

32 kHz watch circuit with programmable

adaptive motor pulse

PCA2000; PCA2001

Measurement of oscillator frequency and inhibit time

The output of the two measuring states can either be

monitored directly at pad RESET or as a modulation of the

supply voltage (a modulating resistor of 30 k

Ω is

connected between VDD and VSS when the signal at

pad RESET is at HIGH-level).

You must follow the supply voltage modulation (see

Fig.10)) in order to guarantee the correct start up of the

circuit during production and testing.

Measuring states:

• State 1: quartz crystal oscillator frequency divided by

1024; state 1 starts with a pulse to VP and ends with a

second pulse to VP

• State 2: inhibit time (see Figs 11 and 12); a signal with

periodicity of 31.25 + n

× 0.122 ms appears at

pad RESET and as current modulation at pad VDD.

Customer testing

Connecting pad RESET to VSS activates the test mode. In

this test mode, the motor output frequency is 8 Hz; the duty

cycle reduction and battery check occurs every second,

instead of every 4 minutes. If the supply voltage drops

below the EOL threshold voltage, the motor output

frequency is 32 Hz with the highest driving level.

EOL of battery

The supply voltage is checked every 4 minutes. If it drops

below the EOL reference (1.38 V for silver-oxide, 2.5 V for

lithium batteries), the motor steps change from one pulse

per second to a burst of four pulses every 4 seconds. The

step detection is switched off, and the motor is driven with

the highest pulse level.

Only the PCA2000 has an EOL function.

VDD

VP(stop)

t(start) > 500 ms

VSS

VDD(nom)

001aaa055

tp(stop)

Fig.10 Supply voltage at start up during production

and testing.

handbook, halfpage

MGW355

VDD

VSS

31.25 ms

+ inhibition time

Fig.11 Output waveform at pad RESET for

instruction state 2.

handbook, halfpage

VDD

VP(start)

VP(mod)

VP(stop)

tp(start)

VSS

VDD(nom)

MGU719

tp(stop)

Fig.12 Supply voltage modulation for starting and

stopping of instruction state 2.

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