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Manufacturer Part #


M41T81S Series 5.5 V I2C / 2-Wire / Serial SMT Real Time Clock - SOIC-8

Product Specification Section
Technical Attributes
Attributes Table
Date Format: DW:DM:M:Y
Time Format: HH:MM:SS:hh
Interface: I2C / 2-Wire / Serial
SRAM Size: 20b
Supply Voltage-Nom: 2.7V to 5.5V
Temperature Grade: Industrial
Operating Temp Range: -40°C to +85°C
Storage Temperature Range: -55°C to +125°C
Package Style:  SOIC-8
Mounting Method: Surface Mount
Features & Applications
The M41T81SM6F is a low power serial real-time clock (RTC) with alarams and a built-in 32.768 KHz oscillator, available in SOIC-8 package.

It has 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.


  • Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
  • 32 kHz crystal oscillator with integrated load capacitance (12.5 pF) which provides exceptional oscillator stability and high crystal series resistance operation)
  • Oscillator stop detection (monitors clock operation)
  • Serial interface supports I2C bus (400 kHz protocol)
  • Ultra-low battery supply current of 0.6 μA (typ)
  • 2.0 to 5.5 V clock operating voltage
  • Automatic switchover and deselect circuitry (fixed reference) which provides full operation in 3.0 V applications)
  • VCC = 2.7 to 5.5 V
  • 2.5 V ≤ VPFD ≤ 2.7 V
  • Power-down time-stamp (HT bit) which allows determination of time elapsed in battery backup
  • Battery low flag
  • 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 for crystal deviation due to temperature)
  • Operating temperature of –40 to 85 °C
  • Package options include an 8-lead SOIC or 18-lead embedded crystal SOIC
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