Description
The M41T8x are low-power serial I2C real-time clocks (RTCs) 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.

FEATUREs
• Ultra-low battery supply current of 365 nA
• Factory-calibrated accuracy of ±5 ppm typical 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
    – M41T83R: VCC = 2.70 V to 5.50 V
    – M41T83Z: VCC = 2.38 V to 5.50 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
• Low operating current of 80 μA
• Oscillator stop detection
• Battery or SuperCap™ backup
• Operating temperature of –40 °C to 85 °C
• Package options
    – a 16-lead QFN (M41T83)
    – an 8-lead SOIC (M41T82) or
    – an 18-lead embedded crystal SOIC (M41T83)
• RoHS compliance: lead-free components are compliant with the RoHS directive