M48T254V-10ZA1

Real Time Clock Overview

The M48T254V is a 16 Mbit (2 Mb x 8 bit) non-volatile static RAM and real-time clock integrated into a single 168-ball PBGA module. Operating at 3.3V with a 100 ns access time, it combines ultra-low power SRAM with a phantom clock interface for precise timekeeping. The device features automatic write protection during power failures and includes an integrated battery and crystal housed in a replaceable SNAPHAT top. It supports data retention for ten years without main power.

Real Time Clock Feature Summary

• Integrated 16 Mbit SRAM with 100 ns read/write access time
• Real-time clock tracking tenths of seconds through years with leap year correction
• Automatic write protection when VCC falls below the power-fail deselect voltage
• Replaceable SNAPHAT housing containing a lithium battery and quartz crystal

Real Time Clock Applications

• Industrial systems requiring persistent timekeeping and data storage
• Telecommunications equipment needing backup memory solutions
• Embedded controllers utilizing phantom clock serial interfaces
• Automotive electronics operating within standard temperature ranges

Real Time Clock Procurement Notes

Verify the specific ordering suffix to confirm package dimensions and temperature range. The ZA suffix indicates a 168-ball BGA module with a 1.27 mm ball pitch. Ensure the SNAPHAT battery top is compatible with the selected variant. Confirm that the application environment remains within the specified 0°C to 70°C operating temperature limits.

Real Time Clock Selection Notes

Select this component when a combined non-volatile memory and real-time clock solution is required in a compact form factor. The phantom clock interface allows time updates via serial bit-streams without dedicated pins. Consider the 10-year data retention capability for long-term deployment scenarios where battery replacement is infrequent or difficult.

Real Time Clock Part Context

This part belongs to the TIMEKEEPER RAM family from STMicroelectronics. It provides a pin-compatible alternative to standard SRAMs while adding real-time clock functionality. The integration of the battery and crystal eliminates external components typically required for non-volatile memory systems.

Real Time Clock Replacement Considerations

Direct replacements must match the 168-ball PBGA package and 100 ns speed. Verify compatibility with the phantom clock protocol if existing software relies on the specific 64-bit pattern recognition sequence. Check if the new component supports the same 3.3V supply and power-fail thresholds.

Real Time Clock FAQ

How does the phantom clock interface function?

It uses a 64-bit serial bit-stream pattern recognized through consecutive WRITE cycles to gain access to the clock registers, allowing time updates via standard memory control signals.

What happens when VCC drops below the power-fail threshold?

The device automatically invokes write protection to prevent data corruption and switches to battery backup mode to maintain SRAM data and RTC operation.

Is the battery replaceable?

Yes, the lithium battery and crystal are housed in a separate SNAPHAT top that can be replaced independently of the PBGA module.