SUMMARY DESCRIPTION
The M41ST85Y/W Serial TIMEKEEPER®/Controller SRAM is a low power 512-bit, static CMOS SRAM organized as 64 words by 8 bits. A built-in 32.768 kHz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 2., page 14) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format.

FEATURES SUMMARY
■ 5.0 OR 3.0V OPERATING VOLTAGE
■ SERIAL INTERFACE SUPPORTS I2C BUS(400 KHz)
■ NVRAM SUPERVISOR FOR EXTERNAL LPSRAM
■ OPTIMIZED FOR MINIMAL INTERCONNECT TO MCU
■ 2.5 TO 5.5V OSCILLATOR OPERATING VOLTAGE
■ AUTOMATIC SWITCH-OVER AND DESELECT CIRCUITRY
■ CHOICE OF POWER-FAIL DESELECT VOLTAGES
– M41ST85Y: VCC= 4.5 to 5.5V; 4.20V ≤VPFD ≤4.50V
– M41ST85W: VCC= 2.7 to 3.6V; 2.55V ≤VPFD ≤2.70V
■ 1.25V REFERENCE (for PFI/PFO)
■ COUNTERS FOR TENTHS/HUNDREDTHS OF SECONDS, SECONDS, MINUTES, HOURS, DAY, DATE, MONTH, YEAR, AND
CENTURY
■ 44 BYTES OF GENERAL PURPOSE RAM
■ PROGRAMMABLE ALARM AND INTERRUPT FUNCTION (VALID EVEN DURING BATTERY BACK-UP MODE)
■ WATCHDOG TIMER
■ MICROPROCESSOR POWER-ON RESET
■ BATTERY LOW FLAG
■ POWER-DOWN TIMESTAMP (HT BIT)
■ ULTRA-LOW BATTERY SUPPLY CURRENT OF 500nA (MAX)
■ PACKAGING INCLUDES A 28-LEAD SOIC AND SNAPHAT® TOP (to be ordered separately)
■ SOIC SNAPHAT PACKAGE PROVIDES DIRECT CONNECTION FOR A SNAPHAT TOP WHICH CONTAINS THE BATTERY
AND CRYSTAL
■ SOIC EMBEDDED CRYSTAL PACKAGE (MX) OPTION
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