PCA2002_5

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 05 — 11 November 2008

5 of 25

NXP Semiconductors

PCA2002

32 kHz watch circuit programmable output period and pulse width

After measuring the effective oscillator frequency, the number of correction pulses must

be calculated and stored together with the calibration period in the OTP memory (see

Section 7.6).

The oscillator frequency can be measured at pad RESET, where a square wave signal

with the frequency of

is provided.

This frequency shows a jitter every minute or every two minutes, depending on the

programmed calibration period, which originates from the time calibration.

Details on how to measure the oscillator frequency and the programmed inhibition time

are given in Section 7.10.

7.3 Reset

At pin RESET an output signal with a frequency of

is provided.

After releasing pin RESET, the first motor pulse is generated exactly one period later with

the opposite polarity to the last pulse before stopping. The debounce time for the reset

function is between 31 ms and 62 ms.

frequency is 32 Hz, which can be used to test the mechanical function of the watch.

7.4 Programming possibilities

The programming data is organized in an array of 8-bit words (see Table 4). A contains the

time calibration, B the setting for the monitor pulses, C is not used and D contains the type

recognition (see Table 7).

Table 3.

Time calibration

Calibration

period

Correction per step (n = 1)

Correction per step (n = 127)

ppm

seconds per day ppm

seconds per day

1 minute

2.03

0.176

258

22.3

2 minutes

1.017

0.088

129

11.15

1

1024

------------

f

osc

×

1

1024

------------

f

osc

×

32Hz

=

Table 4.

Words and bits

Word

Bit

1

2

3

4

5

6

7

8

A

number of 8192 Hz pulses to be removed

calibration

period

B

pulse width

output period

duty

cycle

pulse

stretching

C

D

type

factory test bit