M41T56

The M41T56 TIMEKEEPER^® is a low power, 512- bit static CMOS RAM organized as 64 words by 8 bits. A built-in 32,768Hz oscillator (external crystal controlled) and the first 8 bytes of the RAM are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. Addresses and data are transferred serially via a twoline, bi-directional bus. The built-in address register is incremented automatically after each WRITE or READ data byte.

The M41T56 clock has a built-in power sense circuit which detects power failures and automatically switches to the battery supply during power failures. The energy needed to sustain the RAM and clock operations can be supplied from a small lithium coin cell.

Typical data retention time is in excess of 10 years with a 50mAh, 3V lithium cell. The M41T56 is supplied in an 8-lead Plastic SOIC package or a 28- lead SNAPHAT^® package.

The 28-pin, 330mil SOIC of M41T56 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 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 surfacemounting. The SNAPHAT housing is keyed to prevent reverse insertion. The SOIC and battery/crystal packages are shipped separately in plastic antistatic
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 16., page 22).

Caution: Do not place the SNAPHAT battery/crystal package "M4Txx-BR12SH" in conductive foam as this will drain the lithium button-cell battery.