General description

The PCF2127A 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 PCF2127A has 512 bytes of general purpose static RAM, 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 −15 °C to +60 °C

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

■ Provides year, month, day, weekday, hours, minutes, and seconds

■ 512 bytes of general purpose static RAM

■ Timestamp function

◆ with interrupt capability

◆ detection of two different events on one multilevel input pin (e.g. for tamper detection)

■ Two line bidirectional 400 kHz Fast-mode I2C-bus interface (IOL = 3 mA at pin SDA/CE)

■ 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 pin

■ 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 and system reset pin (open-drain)

■ Programmable 1 second or 1 minute interrupt

■ Programmable countdown timer with interrupt capability

■ Programmable watchdog timer with interrupt and reset capability

■ Programmable alarm function with interrupt capability

■ Programmable square wave open-drain output pin

■ Clock operating voltage: 1.2 V to 4.2 V

■ Low supply current: typical 0.65 μA at VDD = 3.0 V and Tamb = 25 °C

■ Automatic leap year correction

Applications

■ Electronic metering for electricity, water, and gas

■ Timekeeping instruments with high precision

■ GPS equipment to reduce time to first fix

■ Applications that require an accurate process timing

■ Products with long automated unattended operation time