M41T93 Datasheet, PDF (6/49 Pages) STMicroelectronics – Serial SPI bus RTC with battery switchover

Summary description
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Summary description
M41T93
The M41T93 is a low power Serial SPI Bus Real Time Clock with a built-in 32.768kHz
oscillator (external crystal-controlled for the QFN16 package, and embedded crystal for the
SOX18 package). Eight bytes of the Register Map (see Table 3 on page 18) 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 serial SPI bus-compatible interface. The
built-in address register is incremented automatically after each WRITE or READ data byte.
The M41T93 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, Alarm
interrupt, 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 M41T93 is supplied in
either a QFN16 or an SOX18 (MY), 300mil SOIC which includes an embedded 32kHz
crystal. The SOX18 package requires only a user-supplied battery to provide non-volatile
operation.
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