General description

The PCF2129T is a CMOS1 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 very low power consumption. The PCF2129T has a selectable I2C-bus or SPI-bus, a backup battery switch-over circuit, a programmable watchdog function, a timestamp function, and many other features.

Features and benefits

■ Temperature Compensated Crystal Oscillator (TCXO) with integrated capacitors

■ Typical accuracy: ±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 year correction

■ Timestamp function

♦ with interrupt capability

♦ detection of two different events on one multilevel input pin (for example, for tamper detection)

■ 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 output

■ Clock operating voltage: 1.8 V to 4.2 V

■ Low supply current: typical 0.70 μA at VDD = 3.3 V

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