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
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
V
SS
1 ground (0 V) TEST 2 test output OSC IN 3 oscillator input OSC OUT 4 oscillator output V
DD
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
V
SS
TEST
OSC IN
OSC OUT
RESET M2 M1
V
DD
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
DF
= 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
t
P
t
D
t
C
POSSIBLE CORRECTION
SEQUENCE
t
T
M1 - M2
V
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
P3
t = 5.86 ms
P2
t = 7.81 ms
P1
43.75 %
50.00 %
56.25 %
62.50 %
68.75 %
75.00 %
tt
DFDFSOFF
=
t
ONL
t
SOFF
t
DF
t = 977 µs
SON
t
t = 244 µs
SONF
ON
t
=
SON
tt
DF
STAGE 6
Fig.3 Motor pulses (VDD= 1.55 V).
t
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
V
DD
V
SS
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
D
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
t
M1
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.
t
M2
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).
t
M3
3 The switches P1 and P2 remain closed for the time tM3.
t
M4
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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