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  • The M41T66 is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator (external crystal controlled). Eight registers are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 8 registers provide status/control of alarm, square wave, 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, programmable square wave output, and watchdog output. 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 M41T66 is supplied in a 16-pin QFN.

    Key Features

    • Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
    • 32 KHz crystal oscillator integrating load capacitance and high crystal series resistance operation
    • Oscillator stop detection monitors clock operation
    • Serial interface supports I2C bus (400 kHz)
    • 525 nA timekeeping current at 3 V
    • Low operating current of 35 μA (at 400 kHz)
    • Timekeeping down to 1.0 V
    • 1.3 V to 4.4 V I2C bus operating voltage
      • Allows use in lithium ion rechargeable applications
    • 32 KHz square wave on power-up to drive a microcontroller in low-power mode
    • Programmable (1 Hz to 32 KHz) square wave
    • Programmable alarm with interrupt function
    • Accurate programmable watchdog (from 62.5 ms to 31 min)
    • Software clock calibration to compensate deviation of crystal due to temperature
    • Automatic leap year compensation
    • Operating temperature of –40 to 85 °C
    • Lead-free 16-pin QFN package

Circuit Diagram

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Technical Documentation

    • Description Version Size Action
      DS5956
      Serial real-time clock with alarms
      2.0
      411.55 KB
      PDF
      DS5956

      Serial real-time clock with alarms

    • Description Version Size Action
      AN3060
      Applications guide for serial real-time clocks (RTCs)
      3.0
      878.56 KB
      PDF
      AN1011
      Battery technology used in NVRAM and real-time clock (RTC) products from ST
      4.0
      248.17 KB
      PDF
      AN934
      How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products
      4.1
      123.42 KB
      PDF
      AN1216
      Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs)
      2.0
      192.89 KB
      PDF
      AN4641
      Integrating TIMEKEEPER® and real-time clock supervisor functions
      1.0
      479.28 KB
      PDF
      AN923
      Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs
      4.0
      142.23 KB
      PDF
      AN1572
      Power-down time-stamp function in serial real-time clocks (RTCs)
      2.0
      171.31 KB
      PDF
      AN1336
      Power-fail comparator for NVRAM supervisory devices
      2.0
      127.81 KB
      PDF
      AN3060

      Applications guide for serial real-time clocks (RTCs)

      AN1011

      Battery technology used in NVRAM and real-time clock (RTC) products from ST

      AN934

      How to use the digital calibration feature in TIMEKEEPER® and serial real-time clock (RTC) products

      AN1216

      Implementing a periodic alarm with TIMEKEEPER® and serial real-time clocks (RTCs)

      AN4641

      Integrating TIMEKEEPER® and real-time clock supervisor functions

      AN923

      Managing century information using serial real-time clocks and TIMEKEEPER® NVRAMs

      AN1572

      Power-down time-stamp function in serial real-time clocks (RTCs)

      AN1336

      Power-fail comparator for NVRAM supervisory devices

Publications and Collaterals

    • Description Version Size Action
      Serial real-time clock ICs 1.0
      827.11 KB
      PDF

      Serial real-time clock ICs

Quality and Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
M41T66Q6F
Active
VFQFPN 16 3x3x0.9 Industrial Ecopack2

M41T66Q6F

Package:

VFQFPN 16 3x3x0.9

Material Declaration**:

PDF XML

Marketing Status

Active

Package

VFQFPN 16 3x3x0.9

Grade

Industrial

RoHS Compliance Grade

Ecopack2

(**) 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.

Sample & Buy

Part Number
Order from Distributors
Order from ST
Marketing Status
ECCN (US)
ECCN (EU)
Packing Type
Package
Temperature (°C) Budgetary Price (US$)*/Qty
More info
min
max
M41T66Q6F No availability of distributors reported, please contact our sales office Buy now
Active
EAR99 NEC Tape And Reel VFQFPN 16 3x3x0.9 -40 85 0.823 / 1k
MORE INFO

NVRAM size (B):

-

Country of Origin:

MALAYSIA

M41T66Q6F

Marketing Status

Active

ECCN (US)

EAR99

Budgetary Price (US$)*/Qty

0.823 / 1k

ECCN (EU)

NEC

Packing Type

Tape And Reel

Package

VFQFPN 16 3x3x0.9

Operating Temperature (°C)

(min)

-40

(max)

85

Budgetary Price (US$)* / Qty

0.823 / 1k

NVRAM size (B)

-

Country of Origin

MALAYSIA

(*) Suggested Resale Price per unit (USD) for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office  or our Distributors