M41T82_08 Datasheet, PDF (6/58 Pages) STMicroelectronics – Serial I2C bus RTC with battery switchover

Description
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Description
M41T82 M41T83
The M41T8x are low power serial I²C real-time clocks with a built-in 32.768 kHz oscillator
(external crystal-controlled for the QFN16 and SO8 packages, embedded crystal for the
SOX18 package). Eight bytes of the Register Map (see Table 2 on page 23) are used for the
clock/calendar function and are configured in binary coded decimal (BCD) format. An
additional 17 bytes of the Register Map provide status/control of the two Alarms, Watchdog,
8-bit Counter, and Square Wave functions. An additional seven bytes are made available as
user SRAM.
Addresses and data are transferred serially via a two line, bi-directional I²C interface. The
built-in address register is incremented automatically after each WRITE or READ data byte.
The M41T8x 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 clock operations can be supplied by a small lithium button battery
when a power failure occurs.
Functions available to the user include a non-volatile, time-of-day clock/calendar, two Alarm
interrupts, Watchdog Timer, programmable 8-bit Counter, and Square Wave outputs. 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), 30, and 31 day months are made automatically. The M41T83 is supplied in
either a QFN16 (QA) or an SOX18 (MY), 300mil SOIC which includes an embedded 32 KHz
crystal. The SOX18 package requires only a user-supplied battery to provide non-volatile
operation. The M41T82 is available only in an SO8 package.
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