The M48T129Y/V TIMEKEEPER? RAM is a 128 Kb x 8 non-volatile static RAM and real-time clock with programmable alarms and a watchdog timer. The special DIP package provides a fully integrated battery back-up memory and real-time clock solution. The M48T129Y/V directly replaces industry standard 128 Kb x 8 SRAM. It also provides the non-volatility of Flash without any requirement for special WRITE timing or limitations on the number of WRITEs that can be performed.
For surface-mount environments ST provides an equivalent SMT solution consisting of a 44-pin, 330mil SOIC TIMEKEEPER SUPERVISOR (M48T201V/Y) and a 32-pin, (TSOP, 8 x 20mm) 1Mb LPSRAM.
The 44-pin, 330mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT? housing containing the battery.
The unique design allows the SNAPHAT battery 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 damage due to the high temperatures required for device surfacemounting.
The SNAPHAT housing is keyed to prevent reverse insertion. The SNAPHAT battery package is shipped separately in plastic anti-static tubes or in Tape & Reel form. The part number is “M4Txx-BR12SH1” (see Table 18., page 28).
The 32-pin, 600mil DIP Hybrid houses a controller chip, SRAM, quartz crystal, and a long life lithium button cell in a single package.