Serial real-time clock (RTC) with integral backup battery and crystal

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  • The M41T00CAP is a low-power serial real-time clock (RTC) with integral battery and crystal in ST’s 24-pin CAPHAT™ package. It includes a crystal controlled, 32.768 kHz oscillator and has a built-in power sense circuit which detects power failures and automatically switches to the backup battery when a power failure occurs.

    Eight registers comprise the clock/calendar function and are configured in binary-coded decimal (BCD) format. Addresses and data are transferred serially via an industry standard, two line, 400 kHz, bidirectional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The internal lithium coin cell contains ample energy to sustain timekeeping operation for 10 years in the absence of system power. The eight clock address locations contain the century, year, month, date, day, hour, minute, and second in 24-hour BCD format. Corrections for the number of days in a month, including leap year, are made automatically (leap year valid up to year 2100).


    • Real-time clock (RTC) with backup battery integrated into package
    • Uses M41T00S enhanced RTC with precision switchover reference
    • 400 kHz I2C serial interface
    • Automatic switchover and deselect circuitry with fixed reference voltage
      • VCC = 2.7 to 5.5 V operating voltage range
      • 2.6 V (typ) power-fail deselect (switchover) threshold
    • Counters for seconds, minutes, hours, day, date, month, year and century
    • Software clock calibration
    • Low operating current of 300 µA
    • Oscillator stop detection
    • Battery backup
    • Operating temperature of 0 to 70 °C
    • Self-contained battery and crystal in CAPHAT™ DIP package
    • RoHS compliant
      • Lead-free second level interconnect
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      Serial access real-time clock (RTC) with integral backup battery and crystal
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      Serial access real-time clock (RTC) with integral backup battery and crystal

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