M41T81SM6F

M41T81SM6F is a low-power serial real-time clock (RTC) with a built-in 32.768KHz oscillator (external crystal controlled). Eight bytes of the SRAM are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional 12 bytes of SRAM provide status/control of alarm, watchdog and square wave functions. 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 M41T81S 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 supply when a power failure occurs. Functions available to the user include a non-volatile, time-of-day clock/calendar, alarm interrupts, watchdog timer and programmable square wave output.

• Supply voltage range from 2.7 to 5.5V
• Counters for tenths/hundredths of seconds, seconds, minutes, hrs, day, date, month, yr and century
• 32KHz crystal oscillator with integrated load capacitance (12.5pf)
• Oscillator stop detection (monitors clock operation)
• Serial interface supports I2C bus (400KHz protocol)
• Ultra-low battery supply current of 0.6µA (typ) and battery low flag
• Power-down time-stamp (HT bit) which allows determination of time elapsed in battery backup
• Programmable alarm and interrupt function (valid even during battery backup mode)
• Software clock calibration (to compensate for crystal deviation due to temperature)
• 8 lead SO package and temperature range from -40°C to +85°C