Philips PCA1487U, PCA1487U-10, PCA1487U-10-F2, PCA1488U-10-F1, PCA1484T Datasheet

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DATA SH EET

Product speciﬁcation Supersedes data of 1998 Mar 26 File under Integrated Circuits, IC16

1998 Apr 21

INTEGRATED CIRCUITS

PCA148x series

32 kHz watch circuits with adaptive motor pulse

1998 Apr 21 2

Philips Semiconductors Product speciﬁcation

32 kHz watch circuits with adaptive motor pulse

PCA148x series

FEATURES

• 32 kHz oscillator, amplitude regulated with excellent frequency stability

• High immunity of the oscillator to leakage currents

• Time calibration electrically programmable and

reprogrammable (via EEPROM)

• A quartz crystal is the only external component required

• Very low current consumption; typically 170 nA

• Output for bipolar stepping motors of different types

• Up to 50% reduction in motor current compared with

conventional circuits, by self adaption of the motor pulse width in accordance with the required torque of the motor

• No loss of motor steps possible because of on-chip detection of the induced motor voltage

• Indication for battery end-of-life

• Stop function for accurate timing

• Power-on reset for fast testing

• Various test modes for testing the mechanical parts of

the watch and the IC.

GENERAL DESCRIPTION

The PCA148x series devices are CMOS integrated circuits specially suited for battery-operated, quartz-crystal-controlled wrist-watches, with a bipolar stepping motor.

ORDERING INFORMATION

Note

1. Figure 1 and Chapter “Package outline” show details of standard package, available for large orders only. Chapter “Chip dimensions and bonding pad locations” shows exact pad locations for other delivery formats.

TYPE

NUMBER

PACKAGE

(1)

NAME DESCRIPTION VERSION

PCA1485U/7 − chip with bumps on tape − PCA1486U/7 − chip with bumps on tape − PCA1486U/10 − chip on foil − PCA1487U/10 − chip on foil −

PINNING

SYMBOL PIN DESCRIPTION

1 ground (0 V) TEST 2 test output OSC IN 3 oscillator input OSC OUT 4 oscillator output V

5 supply voltage M1 6 motor 1 output M2 7 motor 2 output RESET 8 reset input

Fig.1 Pin configuration, PCA148xT, (PMFP8).

1 2 3 4

8 7 6 5

PCA148xT

TEST

OSC IN

OSC OUT

RESET M2 M1

MSA968

1998 Apr 21 3

Philips Semiconductors Product speciﬁcation

32 kHz watch circuits with adaptive motor pulse

PCA148x series

FUNCTIONAL DESCRIPTION AND TESTING

The motor output delivers pulses of six different stages depending on the torque required to turn the motor (Fig.3). Every motor pulse is followed by a detection phase which monitors the waveform of the induced motor voltage. When a step is missed a correction sequence will be started (Fig.2).

Motor pulses

The circuit produces motor pulses of six different stages (stage 1 to 5, stage 6).

Stages 1 to 5 are used in normal operation, stage 6 occurs under the following conditions:

• Correction pulse after a missing step

• End-of-life mode

• If stage 5 is not enough to turn the motor.

The ON state of the motor pulse varies between 43.75% and 75% of the duty factor t

= 977 µs depending on the

stage (Fig.3). It increases in steps of 6.25% per stage.

After a RESET the circuit always starts and continues with stage 1, when all motor pulses have been executed. A failure to execute all motor pulses results in the circuit going into stage 2, this sequence will be repeated through to stage 6.

When the motor pulses at stage 5 are not large enough to turn the motor, stage 6 is implemented for a maximum of 8 minutes with no attempt to keep current consumption low. After stage 6 has been executed the procedure is repeated from RESET.

The circuit operates for 8 minutes at a fixed stage, if every motor pulse is executed. The next 480 motor pulses are then produced at the next lower stage unless a missing step is detected. If a step is missed a correction sequence is produced and for a maximum of 8 minutes the motor pulses are increased by one stage.

Fig.2 Possible motor output waveform in normal operation with motor connected.

MSA969

MOTOR

PULSE

DETECTION

POSSIBLE CORRECTION

SEQUENCE

M1 - M2

1998 Apr 21 4

Philips Semiconductors Product speciﬁcation

32 kHz watch circuits with adaptive motor

pulse

PCA148x series

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MSA970

STAGE 1

STAGE 2

STAGE 3

STAGE 4

STAGE 5

t = 3.9 ms

t = 5.86 ms

t = 7.81 ms

43.75 %

50.00 %

56.25 %

62.50 %

68.75 %

75.00 %

DFDFSOFF

ONL

SOFF

t = 977 µs

SON

t = 244 µs

SONF

SON

STAGE 6

Fig.3 Motor pulses (VDD= 1.55 V).

OFF

for stage 1 to 6= 611 µs − stage × 61µs

tON for stage 1 to 6= 366 µs + stage × 61µs

1998 Apr 21 5

Philips Semiconductors Product speciﬁcation

32 kHz watch circuits with adaptive motor pulse

PCA148x series

Voltage level detector

The supply voltage is compared with the internal voltage reference V

EOL

every minute. The first voltage level

detection is carried out 30 ms after RESET. When the detected VDD voltage level is greater than V

EOL

the circuit operates in normal mode (Fig.3). If the battery end-of-life is detected (VDD< V

EOL

), the detection and stage control is switched OFF and the waveform of stage 6 will be executed. To indicate this condition the waveform is produced in bursts of 4 pulses every 4 s.

Detection of motor movement

After a motor pulse, the motor is short-circuited to VDD for 1 ms. Afterwards the energy in the motor inductor will be dissipated to measure only the current generated by the induced motor voltage. During the time tDI (dissipation of energy time) all switches shown in Fig.4 are open to reduce the current as fast as possible. The current will now flow through the diodes D3 and D2, or D4 and D1. Then the first of 52 possible measurement cycles (tMC) starts to measure the induced current.

Fig.4 Motor driving and detecting circuit.

MSA941

MOTORM1 M2

N1 D3

P1 D1

L1 L2

N2D4

P2D2

1998 Apr 21 6

Philips Semiconductors Product speciﬁcation

32 kHz watch circuits with adaptive motor pulse

PCA148x series

Detection criteria

The PCA148x uses current detection in two defined parts of the detection phase to determine if the motor has moved (refer to Figs 5 and 6). 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.5).

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 t

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 (V

EOL

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

motor.

Table 1 Measurement cycle

SYMBOL PHASE DESCRIPTION

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.

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.6).

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

4 If the circuit detectsfewer 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.

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