1. General description
The PCA2129 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 PCA2129 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.
For a selection of NXP Real-Time Clocks, see Table 83 on page 73

2. Features and benefits
AEC-Q100 compliant for automotive applications
Operating temperature range from -40 ºC to +85 ºC
Temperature Compensated Crystal Oscillator (TCXO) with integrated capacitors
Typical accuracy: ±3 ppm from -30 ºC to +80 ºC
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
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 uA at VDD = 3.3 V