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Low-power serial real-time clock (RTC) with alarm

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The M41T6x is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator. Eight registers are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional eight registers provide status/control of alarm, 32 kHz output, calibration, and watchdog 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.

Functions available to the user include a time-of-day clock/calendar, alarm interrupts (M41T62/65), 32 kHz output (M41T62/64), programmable square wave output (M41T62/64), and watchdog output (M41T65). 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 M41T6x is supplied in two very small packages: a tiny, 3 x 3 mm 16-pin QFN which requires a user-supplied 32 kHz crystal, and an ultra-small 1.5 x 3.2 mm LCC with embedded crystal - no external crystal is required.

  • 特徴

    • Serial real-time clock (RTC) with alarm functions
      • 400 kHz I²C serial interface
      • Memory mapped registers for seconds, minutes, hours, day, date, month, year, and century
      • Tenths/hundredths of seconds register
    • 350 nA timekeeping current at 3 V
    • Timekeeping down to 1.0 V
    • 1.3 V to 4.4 V I²C bus operating voltage
      • 4.4 V max VCCsuitable for lithium-ion battery operation
    • Low operating current of 35 μA (at 400 kHz I²C speed)
    • 32 kHz square wave output is on at power-up. Suitable for driving a microcontroller in low-power mode. Can be disabled. (M41T62/64)
    • Programmable 1 Hz to 32 kHz square wave output (M41T62/64)
    • Programmable alarm with interrupt function (M41T62/65)
    • 32 kHz crystal oscillator integrates crystal load capacitors, works with high series resistance crystals
    • Oscillator stop detection monitors clock operation
    • Accurate programmable watchdog
      • 62.5 ms to 31 minutes timeout
    • Software clock calibration. Can adjust timekeeping to within ±2 parts per million (±5 seconds per month)
    • Automatic leap year compensation
    • –40 to +85 °C operation
    • Two package options:
      • Very small 3 x 3 mm, lead-free and halogen-free (ECOPACK2) 16-lead QFN
      • Ultra-small 1.5 x 3.2 mm, lead-free and halogen-free (ECOPACK2) 8-pin ceramic leadless chip carrier with embedded 32 kHz crystal - no external oscillator components required (M41T62)


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STMicroelectronics - M41T62

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