PCF2129AT/1,512

Real Time Clock Overview

The PCF2129AT is a CMOS Real Time Clock (RTC) and calendar IC featuring an integrated Temperature Compensated Crystal Oscillator (TCXO) based on a 32.768 kHz quartz crystal. Optimized for high accuracy and low power, it operates within a -40 °C to +85 °C range with typical accuracy of ±3 ppm from -15 °C to +60 °C. The device supports selectable I²C or SPI interfaces, includes a backup battery switch-over circuit, programmable watchdog, timestamp function, and interrupt outputs. It runs on a clock voltage of 1.8 V to 4.2 V with a typical supply current of 0.70 μA at 3.3 V.

Real Time Clock Feature Summary

• Integrated TCXO with 32.768 kHz quartz crystal providing ±3 ppm accuracy (-15 °C to +60 °C)
• Selectable I²C (400 kHz Fast-mode) or SPI (6.5 Mbit/s) interface
• Backup battery switch-over circuit with standard and direct switching modes
• Programmable alarm, watchdog timer, and timestamp functions with interrupt capability

Real Time Clock Applications

• Electronic metering for electricity, water, and gas
• GPS equipment to reduce time to first fix
• Products requiring long automated unattended operation

Real Time Clock Procurement Notes

Verify the specific ordering suffix against NXP documentation to confirm package type and packing method. The AT variant utilizes an SO20 package. Confirm that the intended application environment falls within the specified industrial temperature range of -40 °C to +85 °C.

Real Time Clock Selection Notes

Select the PCF2129AT when high precision timing is required without external crystals. Ensure the system voltage remains between 1.8 V and 4.2 V. Choose this model over the PCF2129T if the operating environment is strictly within -15 °C to +60 °C for optimal ±3 ppm accuracy, or if the SO20 package form factor is preferred.

Real Time Clock Part Context

The PCF2129 series includes the PCF2129T in an SO16 package and the PCF2129AT in an SO20 package. Both share identical core functionality but differ in pin count and physical dimensions. The AT version provides additional pins compared to the T version, though many remain not connected.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.