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

INTEGRATED CIRCUITS

DATA SHEET

PCA148x series

32 kHz watch circuits with adaptive motor pulse

Product specification

1998 Apr 21

Supersedes data of 1998 Mar 26

File under Integrated Circuits, IC16

Philips Semiconductors	Product specification

32 kHz watch circuits with adaptive motor

PCA148x series

pulse

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

ORDERING INFORMATION

∙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.

TYPE		PACKAGE(1)
NUMBER	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	−

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.

PINNING

SYMBOL	PIN	DESCRIPTION
VSS	1	ground (0 V)
TEST	2	test output
OSC IN	3	oscillator input
OSC OUT	4	oscillator output
VDD	5	supply voltage
M1	6	motor 1 output
M2	7	motor 2 output
RESET	8	reset input

VSS	1		8	RESET
TEST	2	PCA148xT	7	M2
	3
OSC IN			6	M1
OSC OUT	4		5	VDD
		MSA968

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

1998 Apr 21

2

Philips Semiconductors	Product specification

32 kHz watch circuits with adaptive motor

PCA148x series

pulse

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 tDF = 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.

MOTOR	DETECTION		POSSIBLE CORRECTION
PULSE			SEQUENCE

VM1 - M2

MSA969

t P t D t C

t T

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

1998 Apr 21

3

_

21 Apr 1998

t SONF = 244 μs

t SON

t DF = 977 μs

t SOFF

t ON = t SON t DF

t ONL

t DF t SOFF

=

STAGE 1

t DF

43.75 %

STAGE 2

50.00 %

STAGE 3

56.25 %

STAGE 4

4

62.50 %

STAGE 5

68.75 %

STAGE 6

t P3 = 3.9 ms

75.00 %

t P2 = 5.86 ms

t P1

= 7.81 ms

MSA970

tOFF for stage 1 to 6 = 611 μs − stage × 61 μs tON for stage 1 to 6 = 366 μs + stage × 61 μs

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

motor adaptive with circuits watch kHz 32 pulse

series PCA148x

Semiconductors Philips

specification Product

Philips Semiconductors	Product specification

32 kHz watch circuits with adaptive motor

PCA148x series

pulse

Voltage level detector

The supply voltage is compared with the internal voltage reference VEOL every minute. The first voltage level detection is carried out 30 ms after RESET.

When the detected VDD voltage level is greater than VEOL, the circuit operates in normal mode (Fig.3).

If the battery end-of-life is detected (VDD < VEOL), 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.

VDD

P1	D1			D2	P2
L1		M1	MOTOR	M2	L2
N1	D3			D4	N2

VSS

MSA941

Fig.4 Motor driving and detecting circuit.

1998 Apr 21

5

Philips Semiconductors	Product specification

32 kHz watch circuits with adaptive motor

PCA148x series

pulse

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 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.6).
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

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