PCA2000CX8: 32 kHz watch circuit with programmable adaptive motor pulse

The PCA2000 and PCA2001 are CMOS integrated circuits for 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 necessary to ensure a correct motor step. Changing the drive current of the motor is achieved by chopping the motor pulse with a variable duty cycle. The pulse width and the range of the variable duty cycle can be programmed to suit different types of motors. The automatic pulse adaptation scheme is based on a safe dynamic detection of successful motor steps.

A pad RESET is provided (used for stopping the motor) for accurate time setting and for accelerated testing of the watch.

The PCA2000 has a battery End Of Life (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.

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

PCA2000CX8: Product Block Diagram
Data Sheets (1)
Name/DescriptionModified Date
32 kHz watch circuit with programmable adaptive motor pulse (REV 9.0) PDF (416.0 kB) PCA2000_200124 Nov 2011
Application Notes (3)
Name/DescriptionModified Date
Programming the PCA200x family of watch ICs (REV 1.0) PDF (301.0 kB) AN1121906 Mar 2015
ESD and EMC sensitivity of IC (REV 1.0) PDF (745.0 kB) AN1085314 Mar 2013
Handling bare die (REV 2.0) PDF (1.6 MB) AN1070616 Jun 2011
Users Guides (1)
Name/DescriptionModified Date
Store and transport requirements (REV 3.0) PDF (325.0 kB) UM1056910 Mar 2015
Ordering Information
ProductStatusPackage versionApplicationFunction
PCA2000CX8/12/1End of LifeNAU000
PCA2000CX8/5/1No Longer ManufacturedNAU000
PCA2000CX8/1No Longer ManufacturedNAU000
Package Information
Product IDPackage DescriptionOutline VersionReflow/Wave SolderingPackingProduct StatusPart NumberOrdering code(12NC)MarkingChemical ContentRoHS / Pb Free / RHFLeadFree Conversion DateMSLMSL LF
PCA2000CX8/12/1Wafer, Sawn on FFC, Non-ConductiveDiscontinuedPCA2000CX8/12/1,00 (9352 934 75005)Standard MarkingPCA2000CX8/12/1Always Pb-freeNANA