The PCF2129 is a CMOS Real Time Clock (RTC) and calendar with an integratedTemperature Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartzcrystal optimized for very high accuracy and very low power consumption. The PCF2129has a selectable I2C-bus or SPI-bus, a backup battery switch-over circuit, aprogrammable watchdog function, a timestamp function, and many other features.

• Operating temperature range from -40 °C to +85 °C
• Temperature Compensated Crystal Oscillator (TCXO) with integrated capacitors
• Typical accuracy:
  • PCF2129AT: ±3 ppm from -15 °C to +60 °C
  • PCF2129T: ±3 ppm from -30 °C to +80 °C
• Integration of a 32.768 kHz quartz crystal and oscillator in the same package
• Provides year, month, day, weekday, hours, minutes, seconds, and leap yearcorrection
• Timestamp function:
  • with interrupt capability
  • detection of two different events on one multilevel input pin (for example, for tamperdetection)
• Two line bidirectional 400 kHz Fast-mode I2C-bus interface
• 3 line SPI-bus with separate data input and output (maximum speed 6.5 Mbit/s)
• Battery backup input pin and switch-over circuitry
• Battery backed output voltage
• Battery low detection function
• Power-On Reset Override (PORO)
• Oscillator stop detection function
• Interrupt output (open-drain)
• Programmable 1 second or 1 minute interrupt
• Programmable watchdog timer with interrupt
• Programmable alarm function with interrupt capability
• Programmable square output
• Clock operating voltage: 1.8 V to 4.2 V
• Low supply current: typical 0.70 μA at VDD = 3.3 V

• Electronic metering for electricity, water, and gas
• Precision timekeeping
• Access to accurate time of the day
• GPS equipment to reduce time to first fix
• Applications that require an accurate process timing
• Products with long automated unattended operation time