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.
Addresses and data are transferred serially via a two-line, bidirectional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The M41T8x 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, two alarm interrupts, 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 M41T83 is supplied in either a QFN16 or an SOX18, 300 mil SOIC which includes an embedded 32 KHz crystal. The SOX18 package requires only a user-supplied battery to provide non-volatile operation. The M41T82 is available only in an SO8 package.
- 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 2ndprogrammable 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
RoHS Compliance Grade
RoHS Compliance Grade
(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.