Description
The M41T8x are low power Serial I2C Real Time Clocks with a built-in 32.768kHz 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.

Features
■ 2.0 to 5.5V clock operating voltage
■ Ultra-low battery supply current of 365nA
■ Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
■ Programmable clock calibration (analog and digital)
■ Automatic switchover and reset output circuitry (fixed reference)
    – M41T83S
        VCC = 3.00V to 5.50V
        (2.85V ≤ VRST ≤ 3.00V)
    – M41T83R
        VCC = 2.70V to 5.50V
        (2.55V ≤ VRST ≤ 2.70V)
    – M41T83Z
        VCC = 2.38V to 5.50V
        (2.25V ≤ VRST ≤ 2.38V)
■ Serial interface supports I2C Bus (400kHz protocol)
■ Programmable alarm with interrupt function (valid even during battery back-up mode)
■ Optional 2nd programmable alarm available
■ Square wave output defaults to 32KHz on power-up (M41T83 only)
■ RESET (RST) output
■ Watchdog timer
■ Programmable 8-bit counter/timer
■ 7 bytes of battery-backed user SRAM
■ Battery low flag
■ Power-down time stamp (HT bit)
■ Low operating current of 80µA
■ Oscillator stop detection
■ Battery or Super-cap™ back-up
■ Operating temperature of –40°C to 85°C
■ Package options include:
    – a 16-lead QFN (M41T83),
    – an 18-lead embedded crystal SOIC (M41T83), or
    – an 8-lead SOIC (M41T82)
■ RoHS compliance: lead-free components are compliant with the RoHS directive.