Description
The M41T81 is a low-power serial RTC with a built-in 32.768 kHz oscillator (external crystal controlled).
   
Features
■ For all new designs other than automotive, use
    M41T81S (contact the ST sales office for
    automotive grade)
■ Counters for tenths/hundredths of seconds,
    seconds, minutes, hours, day, date, month,
    year, and century
■ 32 KHz crystal oscillator integrating load
    capacitance (12.5 pF) providing exceptional
    oscillator stability and high crystal series
    resistance operation
■ Serial interface supports I2C bus (400 kHz
    protocol)
■ Ultra-low battery supply current of 0.6 µA
    (typ at 3 V)
■ 2.0 to 5.5 V clock operating voltage
■ Automatic switch-over and deselect circuitry
    (for 3 V application select M41T81S datasheet)
■ Power-down time stamp (HT bit) allowing
    determination of time elapsed in battery
    backup
■ Programmable alarm and interrupt function
    (valid even during battery backup mode)
■ Accurate programmable watchdog timer (from
    62.5 ms to 128 s)
■ Software clock calibration to compensate
    crystal deviation due to temperature
■ Operating temperature of –40 to 85 °C
■ ECOPACK® package available