M41T56

Summary description

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Summary description

The M41T56 is a low power, Serial Real Time Clock with 56 bytes of NVRAM. 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 two-line, 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

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 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 keyed to prevent reverse insertion.

The SOIC and battery/crystal packages 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 16 on page 26).

Caution:

Do not place the SNAPHAT battery/crystal package “M4Txx-BR12SH” in conductive foam

as this will drain the lithium button-cell battery.

Figure 1.

Logic diagram

AI02304B

OSCI

VCC

M41T56

VSS

SCL

OSCO

SDA

FT/OUT

VBAT