PCF85053ATKJ

Real Time Clock Overview

The PCF85053ATKJ is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption, featuring automatic switching to battery backup upon primary power loss. It includes two independent I2C buses with a maximum clock frequency of 400 kHz and supports a clock timeout of 35 ms. The device provides 128 bytes of battery-backed SRAM and an active-low ALRT interrupt output. Operating within a supply voltage range of 1.7 V to 3.6 V and a battery voltage range of 1.55 V to 3.6 V, it utilizes a 32.768 kHz quartz crystal oscillator with integrated load capacitors configurable at 6 pF, 7 pF, or 12.5 pF.

Real Time Clock Feature Summary

• Dual I2C interfaces: Primary bus allows full read/write access to RTC and SRAM registers; secondary bus enables read/write capability gated by the primary controller.
• Integrated 128-byte battery-backed SRAM accessible via dedicated I2C address (1010 111), clearable via the RTC_CLR pin.
• Configurable crystal load capacitors (CL = 6 pF, 7 pF, or 12.5 pF) and programmable offset register for time accuracy adjustment.
• Supports binary/BCD modes, 12-hour/24-hour formats, and daylight savings mode with MC146818B register alignment.

Real Time Clock Applications

• Server and computer precision timekeeping
• Servers with bootable CPU architectures
• Systems utilizing dual I2C architecture
• Network-powered and industrial electronics
• White goods requiring long automated unattended operation

Real Time Clock Procurement Notes

Verify the ordering suffix 'J' corresponds to the REEL 13" Q1/T1 packing method with a minimum order quantity of 6000 units as specified in the manufacturer's ordering information. Confirm that the HVSON12 package dimensions (3 mm x 3 mm x 0.85 mm body) align with the target PCB footprint requirements.

Real Time Clock Selection Notes

Select this component when a bootable CPU RTC with dual I2C isolation is required. Ensure the design accommodates the HVSON12 package with a 0.5 mm pitch. Verify that the system can support the specific I2C device addresses for RTC (1101 111) and SRAM (1010 111). Check if the integrated oscillator capacitors match the external crystal specifications to avoid adding external components.

Real Time Clock Part Context

The PCF85053ATKJ belongs to the PCF85053A series from NXP Semiconductors. It is designed specifically for server applications where precise timekeeping and separation between CPU and BMC communication paths are critical. The device replaces standard RTCs by offering dedicated SRAM and dual-bus functionality in a compact thermal enhanced very thin small outline package.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Designers should verify compatibility with existing firmware drivers due to the specific dual-I2C control bits (TWO, MWO, XCLK) which may differ from single-bus RTC alternatives.