The Dallas Semiconductor DS1228 NVSRAM integrates a 64k nonvolatile static RAM, a full function real time clock, and a lithium battery in a single 28-pin DIP package. The device has a self-contained lithium energy source and control circuitry which constantly monitors VCC. If a power failure occurs, the device automatically write-protects itself, and retains data in the SRAM and RTC. The lithium battery provides nonvolatility in the absence of power.

Applications:

• Industrial Controls
• Data Logging
• Point-of-Sale Terminals
• Networking Equipment
• Medical Instruments
• Telecommunications Systems

Features:

• Integrated Real-Time Clock (RTC) and 64k NVSRAM.
• RTC tracks time in years, months, days, date, hours, minutes, and seconds.
• Automatic power-fail chip enable and write protection.
• Lithium battery backup provides data retention for over 10 years.
• Optional industrial temperature range available.
• Simple interface with standard microprocessor.
• Write protect voltage (VPF = 4.25V)
• Read and write access times of 150 ns

Benefits:

• Single package solution combines RTC and NVSRAM functionality, saving board space and simplifying design.
• Accurate timekeeping even during power outages.
• Reliable data retention prevents data loss during power failures.
• Eliminates the need for external battery and RTC components.

Additional Details:

The DS1228 operates over a voltage range of 4.5V to 5.5V. It is available in a 28-pin DIP package. The clock registers contain century, year, month, day, date, hour, minute, and second information. The end-of-month date is automatically adjusted for months with fewer than 31 days, including correction for leap year. The device includes alarm capabilities. The DS1228 is ideal for applications requiring both real-time clock functionality and nonvolatile memory.