Description
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 21) 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
■ Ultra-low battery supply current of 365 nA
■ Factory calibrated accuracy ±5 ppm guaranteed after 2 reflows (SOX18)
    – Much better accuracies achievable using built-in programmable analog and digital calibration circuits
■ 2.0 V to 5.5 V clock operating voltage
■ Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
■ Automatic switchover and reset output circuitry (fixed reference)
    – M41T83S
        VCC = 3.00 V to 5.50 V
        (2.85 V ≤ VRST ≤ 3.00 V)
    – M41T83R
        VCC = 2.70 V to 5.50 V
        (2.55 V ≤ VRST ≤ 2.70 V)
    – M41T83Z
        VCC = 2.38 V to 5.50 V
        (2.25 V ≤ VRST ≤ 2.38 V)
■ Serial interface supports I2C bus (400 kHz protocol)
■ Programmable alarm with interrupt function (valid even during battery backup mode)
■ Optional 2nd programmable alarm available
■ Square wave output defaults to 32 KHz 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 80 µA
■ Oscillator stop detection
■ Battery or SuperCap™ backup
■ 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