M48T251Y Datasheet - STMicroelectronics

SUMMARY DESCRIPTION
The M48T251Y/V TIMEKEEPER® RAM is a 512Kbit x 8 non-volatile static RAM and real time clock organized as 524,288 words by 8 bits. The special DIP package provides a fully integrated battery back-up memory and real time clock solution. In the event of power instability or absence, a self-contained battery maintains the timekeeping operation and provides power for a CMOS static RAM. Control circuitry monitors VCC and invokes write protection to prevent data corruption in the memory and RTC.

FEATURES SUMMARY
■ 5.0V OR 3.3V OPERATING VOLTAGE
■ REAL TIME CLOCK KEEPS TRACK OF TENTHS/HUNDREDTHS OF SECONDS, SECONDS, MINUTES, HOURS, DAYS, DATE OF THE MONTH, MONTHS, AND YEARS
■ AUTOMATIC LEAP YEAR CORRECTION VALID UP TO THE YEAR 2100
■ AUTOMATIC SWITCH-OVER AND DESELECT CIRCUITRY
■ CHOICE OF POWER-FAIL DESELECT VOLTAGES: (VPFD = Power-fail Deselect Voltage):
   – M48T251Y: 4.25V ≤ VPFD ≤ 4.50V
   – M48T251V: 2.80V ≤ VPFD ≤ 2.97V
■ FULL 10% VCC OPERATING RANGE
■ OVER 10 YEARS’ DATA RETENTION IN THE ABSENCE OF POWER
■ WATCH FUNCTION IS TRANSPARENT TO RAM OPERATION
■ 512K x 8 NV SRAM DIRECTLY REPLACES VOLATILE STATIC RAM OR EEPROM