PCA2002CX8SLASH5SLASH1 datasheet(10/25 Pages) NXP

10 / 25 page

PCA2002_5

Product data sheet

Rev. 05 — 11 November 2008

10 of 25

NXP Semiconductors

PCA2002

32 kHz watch circuit programmable output period and pulse width

7.9 Frequency tuning at assembled watch

Figure 7 shows the test set-up for frequency tuning the assembled watch.

7.10 Measurement of the oscillator frequency and the inhibition time

The output of the two measuring states can either be monitored directly at pin RESET or

as a modulation of the supply current (a modulating resistor of 30 k

Ω is connected

between VDD and VSS when the signal at pin RESET is at HIGH-level).

The supply voltage modulation must be followed as shown in Figure 4 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; inhibition time has a value of n

× 0.122 ms. A signal with the periodicity of

31.25 ms + n

× 0.122 ms appears at pin RESET and as current modulation at pin V

(see Figure 8 and Figure 9)

Fig 7.

Frequency tuning the assembled watch

mgw568

FREQUENCY

COUNTER

PROGRAMMABLE

DC POWER SUPPLY

PC INTERFACE

motor

32 kHz

PCA200x

battery

Fig 8.

Output waveform at pin RESET for instruction state 2

mgw355

VDD

VSS

31.25 ms

+ inhibition time

VO(dif)

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