Philips PCA2000, PCA2001 Technical data

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INTEGRATED CIRCUITS

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PCA2000; PCA2001

32 kHz watch circuit with programmable adaptive motor pulse

Product speciﬁcation Supersedes data of 2003 Feb 04

2003 Dec 17

Philips Semiconductors Product speciﬁcation

32 kHz watch circuit with programmable adaptive motor pulse

FEATURES

• Amplitude-regulated 32 kHz quartz crystal oscillator, with excellent frequency stability and high immunity to leakage currents

• Electrically programmable time calibration with 1 ppm resolution stored in One Time Programmable (OTP) memory

• The quartz crystal is the only external component connected

• Very low power consumption, typical 90 nA

• One second output pulses for bipolar stepping motor

• Minimum power consumption for the entire watch, due

to self adaptation of the motor drive according to the required torque

• Reliable step detection circuit

• Motor pulse width, pulse modulation, and pulse

adaptation rangeprogrammable in a wide range, stored in OTP memory

• Stopfunction for accuratetimesetting and power saving during shelf life

• End Of Life (EOL) indication for silver oxide or lithium battery (only the PCA2000 has the EOL feature)

• Test mode for accelerated testing of the mechanical parts and the IC.

PCA2000; PCA2001

GENERAL DESCRIPTION

The PCA2000; PCA2001 are CMOS integrated circuitsfor battery operated wrist watches with a 32 kHz quartz crystal as timing element and a bipolar 1 Hz stepping motor. The quartz crystal oscillator and the frequency divider are optimized for minimum power consumption. A timing accuracy of 1 ppm is achieved with a programmable, digital frequency adjustment.

To obtain the minimum overall power consumption for the watch, an automatic motor pulse adaptation function is provided. The circuit supplies only the minimum drive current,which is necessarytoensure a correctmotor step. Changing the drive current of the motor is achieved by chopping the motor pulse with a variable duty cycle. The pulsewidth and the range of the variable duty cycle can be programmedtosuit different types of motor. Theautomatic pulse adaptation scheme is based on a safe dynamic detection of successful motor steps.

Apad RESET is provided(used for stoppingthe motor) for accurate time setting and for accelerated testing of the watch.

The PCA2000 has a battery EOL warning function. If the battery voltage drops below the EOL threshold voltage (which can be programmed for silver oxide or lithium batteries), the motor steps change from one pulse per second to a burst of four pulses every 4 seconds.

APPLICATIONS

• Driver circuits for bipolar stepping motors

• High immunity motor drive circuits.

ORDERING INFORMATION

TYPE NUMBER

NAME DESCRIPTION VERSION

PCA2000U/AA − bare die; chip in tray − PCA2001U/AA − bare die; chip in tray − PCA2000U/10AA − bare die; chip on ﬁlm frame carrier − PCA2001U/10AA − bare die; chip on ﬁlm frame carrier −

The PCA2001 uses the same circuit as the PCA2000, but without the EOL function.

PACKAGE

2003 Dec 17 2

Philips Semiconductors Product speciﬁcation

32 kHz watch circuit with programmable adaptive motor pulse

BLOCK DIAGRAM

DD SS

3 4

5 1

OSCILLATOR

VOLTAGE DETECTOR,

OTP-CONTROLLER

÷4

TIMING ADJUSTMENT,

EOL

PCA2000 only

PCA2000 PCA2001

OSCIN

OSCOUT

V V

TEST

8 kHz

INHIBITION

OTP-MEMORY

32 Hz

DIVIDER RESET

MOTOR CONTROL WITH

ADAPTIVE PULSE MODULATION

DETECTION

STEP

PCA2000; PCA2001

RESET

reset

1 Hz

PINNING

SYMBOL PAD DESCRIPTION

1 ground TEST 2 test output OSCIN 3 oscillator input OSCOUT 4 oscillator output V

5 supply voltage MOT1 6 motor 1 output MOT2 7 motor 2 output RESET 8 reset input

Fig.1 Block diagram.

handbook, halfpage

OSCOUT

TEST

OSCIN

mgw567

MOT2MOT1

PCA2000 PCA2001

MGU554

Fig.2 Pad configuration.

RESET

MOT2

MOT1

2003 Dec 17 3

Philips Semiconductors Product speciﬁcation

32 kHz watch circuit with programmable adaptive motor pulse

FUNCTIONAL DESCRIPTION Motor pulse

The motor output supplies pulses of different driving stages, depending on the torque required to turn on the motor. The number of different stages can be selected between three and six. With the exception of the highest driving stage, each motor pulse (tp in Figs 3 and 6) is followed by a detection phase during which the motor movement is monitored, in order to check whether the motor has turned correctly or not.

If a missing step is detected, a correction sequence is generated (see Fig.3) and the driving stage is switched to the next level. The correction sequence consists of two pulses: first a short pulse in the opposite direction (0.98 ms, modulated withthe maximumduty cycle) to give the motor a defined position, followed by a motor pulse of the strongest driving level. Every 4 minutes, the driving level is lowered again by one stage.

The motor pulse has a constant pulse width. The driving level is regulated by chopping the driving pulse with a variable duty cycle. The driving level starts from the programmedminimumvalue and increases by6.25%after each failed motor step. The strongest driving stage, which is not followed by a detection phase, is programmed separately.

PCA2000; PCA2001

Therefore, it is possible to program a larger energy gap between the pulses with step detection and the strongest, not monitored, pulse. This might be necessary to ensure a reliable and stable operation under adverse conditions (magnetic fields, vibrations). If the watch works in the highest driving stage, the driving level jumps after the 4-minute period directly to the lowest stage, and not just one stage lower.

To optimize the performance for different motors, the following parameters can be programmed:

• Pulse width: 0.98 to 7.8 ms in steps of 0.98 ms

• Duty cycle of lowest driving level: 37.5% to 56.25% in

steps of 6.25%

• Number of driving levels (including the highest driving level): 3 to 6

• Duty cycle of the highest driving level: 75% or 100%

• Enlargement pulse forthe highestdriving level: on or off.

The enlargement pulse has a duty cycle of 25% and a pulse width which is twice the programmed motor pulse width. The repetition period for the chopping pattern is

0.98 ms. Figure 4 shows an example of a 3.9 ms pulse.

handbook, full pagewidth

1.96 ms

detection phase

31.25 ms

0.98 ms

31.25 ms

Fig.3 Correction sequence after failed motor step.

2003 Dec 17 4

MGW350

Philips Semiconductors Product speciﬁcation

32 kHz watch circuit with programmable adaptive motor pulse

handbook, full pagewidth

DUTY CYCLE

37.5%

43.75%

50%

56.25%

62.5%

68.75%

75%

81.25%

0.244 ms 0.122 ms

PCA2000; PCA2001

100%

Fig.4 Possible modulations for a 3.9 ms motor pulse.

Step detection

Figure 5 shows a simplified diagram of the motor driving and step detection circuit, and Fig.6 shows the step detection sequence and corresponding sampling current. Betweenthe motor driving pulses,theswitches P1 and P2 are closed, which means the motor is short-circuited. For a pulse in one direction, P1 and N2 are open, and P2 and N1 are closed with the appropriate duty cycle; for a pulse inthe opposite direction, P2 and N1 are open, and P1 and N2 closed.

Thestep detection phaseisinitiated after themotor driving pulse (see Fig.3). P1 and P2 are first closed for 0.98 ms and then 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.

0.98 ms0.98 ms0.98 ms 0.98 ms

MGW351

The induced current caused by the residual motor movement is thensampled 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 Fig.6).

The condition fora successful motorstep is a positive step detection pulse (current in the same direction as in the driving phase) followed by a negative detection pulse withinagiven time limit. This timelimitcanbeprogrammed between 3.9 and 10.7 ms (in steps of 0.98 ms) in order to ensure a safe and correct step detection under all conditions (for instance magnetic fields). The step detection phase stops after the last 31.25 ms, after the start of the motor driving pulse.

2003 Dec 17 5

Philips Semiconductors Product speciﬁcation

32 kHz watch circuit with programmable adaptive motor pulse

handbook, full pagewidth

MOT1

Fig.5 Simplified diagram of motor driving and step detection circuit.

MOTOR

PCA2000; PCA2001

P4P3

MOT2

MGW352

handbook, full pagewidth

MOT

sampling

voltage

sampling

voltage

0.98 ms

(motor shorted)

sampling results

phase 1

phase 2

positive detection

motor shorted

phase 3

td = 0.98 ms

sampling

61 µs

phase 4

programmable time limit

OTP C4 to C6

negative detection

0.49 ms

positive detection level

negative detection level

MGW569

Fig.6 Step detection sequence and corresponding sampling voltage.

2003 Dec 17 6

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