The PCF2127 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 PCF2127has 512 bytes of general-purpose static RAM, a selectable I2C-bus or SPI-bus, a backupbattery switch-over circuit, a programmable watchdog function, a timestamp function, andmany other features.

• UL Recognized Component
• Operating temperature range from -40 °C to +85 °C
• Temperature Compensated Crystal Oscillator (TCXO) with integrated capacitors
• Typical accuracy:
  • PCF2127AT: ±3 ppm from -15 °C to +60 °C
  • PCF2127T: ±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
• 512 bytes of general-purpose static RAM
• 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
• Extra power fail detection function with input and output pins
• 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 wave output pin
• Programmable countdown timer with interrupt
• 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

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