PCA2002 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 8 — 25 November 2011 6 of 30
NXP Semiconductors
PCA2002
32 kHz watch circuit with 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 8.6
).
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 8.10
.
8.3 Reset
At pin RESET an output signal with a frequency of is provided.
Connecting pin RESET to V
DD
stops the motor drive and opens the motor switches.
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.
Connecting pin RESET to V
SS
activates the test mode. In this mode the motor output
frequency is 32 Hz, which can be used to test the mechanical function of the watch.
8.4 Programming possibilities
The programming data is organized in an array of 8-bit words (see Table 5): Word A
contains the time calibration, word B the setting for the monitor pulses, word C is not used
and word D contains the type recognition.
Table 4. 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 5. 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
