1 General description

The PCF2131 is a CMOS Real Time Clock (RTC) and calendar with an integrated Temperature Compensated

Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz crystal optimized for very high accuracy and ultra low

power consumption. The PCF2131 has a selectable I2C-bus or SPI-bus, a backup battery switch-over circuit, a

programmable watchdog function, four timestamps function, and many other features.

2 Features and benefits

• Operating temperature range from -40 °C to +85 °C

• Temperature Compensated Crystal Oscillator (TCXO) with trimmed integrated capacitors

• Ultra low supply current: typical 64 nA at VDD = 3.3 V

• Temperature compensated RTC, typical accuracy ±3 ppm from -40 °C to +85 °C

• Integration of a 32.768 kHz quartz crystal and oscillator in the same package

• Provides year, month, day, weekday, hours, minutes, seconds and 1/100 seconds

• Provides leap year correction

• Timestamp function

– with interrupt capability

– detection of four different events on four input pins (for example, for tamper detection)

• 2-line bidirectional 400 kHz Fast-mode I2C-bus interface

• 4-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 (POR)

• Power-On Reset Override (PORO) function

• Software reset function

• Two interrupt outputs (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: 1.2 V to 5.5 V

3 Applications

• 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