PCA1461 データシートの表示（PDF） - NXP Semiconductors.

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PCA1461

32 kHz watch circuits with adaptive motor pulse

NXP Semiconductors. 

Philips Semiconductors

32 kHz watch circuits with adaptive motor

pulse

Product specification

PCA146x series

Detection criteria

The PCA146x uses current detection in two defined parts

of the detection phase to determine if the motor has moved

(refer to Figs 6 and 7). The detection criteria are:

part 1

• Minimum value of P = 1; where P = number of

measured positive current polarities after tDI.

part 2

• Minimum value of N = 2; where N = number of

measured positive current polarities since the first

negative current polarity after part 1 was detected

(see Fig.6).

If the opposite polarity is measured in one part, the internal

counter is reset, so the results of all measurements in this

part are ignored.

The waveform of the induced current must enable all these

measurements within the time tD after the end of a positive

motor pulse in order to be accepted as a waveform of an

executed motor pulse.

If the detection criterion is satisfied earlier, a measurement

cycle will not be started and the switches P1 and P2 stay

closed, the motor is switched to VDD.

Every measurement cycle (tMC) has 4 phases. These are

detailed in Table 1.

Note that detection and pulse width control will be switched

OFF when the battery voltage is below the end-of-life

voltage (VEOL), or if stage 5 is not sufficient to turn the

motor.

Table 1 Measurement cycle

SYMBOL PHASE

DESCRIPTION

tM1

1 During tM1 the switches P1 and P2 are closed in order to switch the motor to VDD, so the

induced current flows unaffected through the motor inductance.

tM2

2 Measures the induced current; during a maximum time tM2 all switches are open until a change

is sensed by one of the level detectors (L1, L2). The motor is short-circuited to VDD.

Depending on the direction of the interrupted current:

• The current flows through diodes D3 and D2, causing the voltage at M1 to decrease in relation

to M2;

• The current flows through diodes D4 and D1, causing the voltage at M2 to decrease in relation

to M1.

A successfully detected current polarity is normally characterized by a short pulse of

0.5 to 10 µs with a voltage up to ±2.1 V, failed polarity detection by the maximum pulse width of

61 µs and a voltage of ±0.5 V (see Fig.7).

tM3

3 The switches P1 and P2 remain closed for the time tM3.

tM4

4 If the circuit detects fewer pulses than P and N respectively, a pulse of the time tM4 occurs to

reduce the induced current. Therefore P2 and P1 are opened and N1 and N2 are closed.

Otherwise P1 and P2 remain closed.

1998 Apr 21

8

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