M41ST84W

The M41ST84Y/W Serial supervisory TIMEKEEPER ^® 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 9, page 16) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 12 bytes of RAM provide status/control of Alarm, Watchdog and Square Wave functions. Addresses and data are transferred serially via a two line, bi-directional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.

The M41ST84Y/W has a built-in power sense circuit which detects power failures and automatically switches to the battery supply when a power failure occurs. The energy needed to sustain the SRAM and clock operations can be supplied by a small lithium button-cell supply when a power failure occurs. Functions available to the user include  a non-volatile, time-of-day clock/calendar, Alarm interrupts, Watchdog Timer and programmable Square Wave output. Other features include a Power-On Reset as well as an additional input (RSTIN) which can also generate an output Reset (RST). The eight clock address locations contain the century, year, month, date, day, hour, minute, second and tenths/hundredths of a second in 24 hour BCD format. Corrections for 28, 29 (leap year - valid until year 2100), 30 and 31 day months are made automatically.

The M41ST84Y/W is supplied in a 28-lead SOIC SNAPHAT^® package (which integrates both crystal and battery in a single SNAPHAT top) or a 16- pin SOIC. The 28-pin, 330mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT housing containing the battery and crystal. The unique design allows the SNAPHAT battery/crystal package to be mounted on top of the SOIC package after the completion of the surface mount process. Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface- mounting. The SNAPHAT housing is also keyed to prevent reverse insertion.

The 28-pin SOIC and battery/crystal packages of M41ST84Y/W are shipped separately in plastic anti-static tubes or in Tape & Reel form. For the 28-lead SOIC, the battery/ crystal package (e.g., SNAPHAT) part number is "M4TXX-BR12SH" (see Table 20, page 29). Caution: Do not place the SNAPHAT battery/crystal top in conductive foam, as this will drain the lithium button-cell battery.