PCA2002CX8SLASH5SLASH1 datasheet(4/25 Pages) NXP

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PCA2002_5

Product data sheet

Rev. 05 — 11 November 2008

4 of 25

NXP Semiconductors

PCA2002

32 kHz watch circuit programmable output period and pulse width

Functional description

7.1 Motor pulse

The motor driver delivers pulses with an alternating polarity. The output waveform across

the motor terminals is illustrated in Figure 3. Between the motor pulses, both terminals are

connected to VDD which means that the motor is short-circuit.

The following parameters can be selected and are stored in a One Time Programmable

(OTP) memory:

• Output periods of 1 s, 5 s, 10 s, 20 s and 30 s

• Pulse width (tp) between 0.98 ms and 7.8 ms in steps of 0.98 ms

• Full or chopped (75 %) output pulse

• Pulse stretching: an enlargement pulse is added to the primary motor pulse. This

enlargement pulse has a duty cycle of 25 % and a width which is twice the

programmed motor pulse width.

7.2 Time calibration

The quartz crystal oscillator has an integrated capacitance of 5.2 pF, which is lower than

the speciﬁed capacitance (CL) of 8.2 pF for the quartz crystal (see Table 9). Therefore, the

oscillator frequency is typically 60 ppm higher than 32.768 kHz. This positive frequency

offset is compensated by removing the appropriate number of 8192 Hz pulses in the

divider chain (maximum 127 pulses), every 1 or 2 minutes. The time correction is given in

Table 3.

Fig 3.

Motor output waveforms

full pulse

mgu718

chopped

pulse

full pulse

with stretching

chopped pulse

with stretching

period

2tp

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