PCA2000_2001_5

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 05 — 11 November 2008

4 of 28

NXP Semiconductors

PCA2000; PCA2001

32 kHz watch circuit with programmable adaptive motor pulse

6.2 Pin description

7.

Functional description

7.1 Motor pulse

The motor output supplies pulses of different driving stages, depending on the torque

required to turn on the motor. The number of different stages can be selected between

Figure 3 and Figure 6) is followed by a detection phase during which the motor movement

is monitored, in order to check whether the motor has turned correctly or not.

If a missing step is detected, a correction sequence is generated (see Figure 3) and the

driving stage is switched to the next level. The correction sequence consists of two pulses:

first a short pulse in the opposite direction (0.98 ms, modulated with the maximum duty

cycle) to give the motor a defined position, followed by a motor pulse of the strongest

driving level. Every 4 minutes, the driving level is lowered again by one stage.

The motor pulse has a constant pulse width. The driving level is regulated by chopping the

driving pulse with a variable duty cycle. The driving level starts from the programmed

minimum value and increases by 6.25 % after each failed motor step. The strongest

driving stage, which is not followed by a detection phase, is programmed separately.

Table 2.

Pin description

Symbol

Pin

Description

1

ground

i.c.

2

internally connected

OSCIN

3

oscillator input

OSCOUT

4

oscillator output

5

supply voltage

MOT1

6

motor 1 output

MOT2

7

motor 2 output

RESET

8

reset input

Fig 3.

Correction sequence after failed motor step

31.25 ms

1.96 ms

detection phase

31.25 ms

0.98 ms

mgw350