M41T94(2003) View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M41T94 Datasheet PDF : 31 Pages
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M41T94
SUMMARY DESCRIPTION
The M41T94 Serial TIMEKEEPER® SRAM is a
low power, 512-bit static CMOS SRAM organized
as 64 words by 8 bits. A built-in 32,768 Hz oscilla-
tor (external crystal controlled) and 8 bytes of the
SRAM (see Table 10, page 17) are used for the
clock/calendar function and are configured in bina-
ry coded decimal (BCD) format.
An additional 12 bytes of RAM provide status/con-
trol of Alarm, Watchdog and Square Wave func-
tions. Addresses and data are transferred serially
via a serial SPI interface. The built-in address reg-
ister is incremented automatically after each
WRITE or READ data byte. The M41T94 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 sup-
ply when a power failure occurs. Functions avail-
able 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 two
additional debounced inputs (RSTIN1 and
RSTIN2) 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 ninth clock address loca-
tion controls user access to the clock information
and also stores the clock software calibration set-
ting.
The M41T94 is supplied in either a 16-lead plastic
SOIC (requiring user supplied crystal and battery)
or a 28-lead SOIC SNAPHAT® package (which in-
tegrates both crystal and battery in a single
SNAPHAT top). The 28-pin, 330mil SOIC provides
sockets with gold plated contacts at both ends for
direct connection to a separate SNAPHAT hous-
ing containing the battery and crystal. The unique
design allows the SNAPHAT battery/crystal pack-
age to be mounted on top of the SOIC package af-
ter 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 sur-
face-mounting. The SNAPHAT housing is also
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 bat-
tery/crystal package (e.g., SNAPHAT) part num-
ber is “M4TXX-BR12SH” (see Table 21, page 29).
Caution: Do not place the SNAPHAT battery/crys-
tal top in conductive foam, as this will drain the lith-
ium button-cell battery.
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