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M41T11
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SUMMARY DESCRIPTION
The M41T11 TIMEKEEPER RAM is a low power
512-bit, static CMOS RAM organized as 64 words
by 8 bits. A built-in 32.768kHz 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 M41T11 clock has a built-in power sense cir-
cuit which detects power failures and automatical-
ly 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 5 years
with a 50mA/h 3V lithium cell. The M41T11 is sup-
plied in 8 lead Plastic Small Outline package or 28
lead SNAPHAT package.
The 28-pin, 330mil SOIC provides sockets with
gold plated contacts at both ends for direct con-
nection to a separate SNAPHAT housing contain-
ing 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. Inser-
tion of the SNAPHAT housing after reflow pre-
vents potential battery and crystal damage due to
the high temperatures required for device surface-
mounting. The SNAPHAT housing is keyed to pre-
vent reverse insertion. The SOIC and battery/crys-
tal packages are shipped separately in plastic anti-
static tubes or in Tape & Reel form.
For the 28-lead SOIC, the battery/crystal package
(i.e. SNAPHAT) part number is “M4Txx-BR12SH”
Caution: Do not place the SNAPHAT battery/crys-
tal package “M4Txx-BR12SH” in conductive foam
since this will drain the lithium button-cell battery.
Figure 3. Logic Diagram
Table 1. Signal Names
AI01000
OSCI
VCC
M41T11
VSS
SCL
OSCO
SDA
FT/OUT
VBAT
OSCI
Oscillator Input
OCSO
Oscillator Output
FT/OUT
Frequency Test / Output Driver
(Open drain)
SDA
Serial Data Address Input / Output
SCL
Serial Clock
VBAT
Battery Supply Voltage
VCC
Supply Voltage
VSS
Ground