PCA2000USLASHAB datasheet(6/28 Pages) NXP

6 / 28 page

PCA2000_2001_5

Product data sheet

Rev. 05 — 11 November 2008

6 of 28

NXP Semiconductors

PCA2000; PCA2001

32 kHz watch circuit with programmable adaptive motor pulse

The step detection phase is initiated after the motor driving pulse. In phase 1 P1 and P2

are ﬁrst closed for 0.98 ms and then in phase 2 all four drive switches (P1, N1, P2 and N2)

are opened for 0.98 ms. As a result, the energy stored in the motor inductance is reduced

as fast as possible.

The induced current caused by the residual motor movement is then sampled in phase 3

(closing P3 and P2) and in phase 4 (closing P1 and P4). For step detection in the opposite

direction P1 and P4 are closed during phase 3 and P2 and P3 during phase 4 (see

Figure 6).

Fig 5.

Simpliﬁed diagram of motor driving and step detection circuit

Fig 6.

Step detection sequence and corresponding sampling voltage

mgw352

VDD

VSS

MOTOR

MOT1

MOT2

mgw569

td = 0.98 ms

0.98 ms

(motor shorted)

sampling

voltage

Imotor

sampling

voltage

positive detection level

negative detection level

programmable time limit

OTP C4 to C6

sampling

positive detection

negative detection

sampling results

motor shorted

sampling

µs

0.49 ms

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