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

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.

Key Features

  • Serial real-time clock (RTC) with alarm functions
    • 400 kHz I2 C 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 I2 C bus operating voltage
    • 4.4 V max VCC suitable for lithium-ion battery operation
  • Low operating current of 35 μA (at 400 kHz I2 C 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 min 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 & halogen-free (ECOPACK2® ) 16-lead QFN
    • Ultra-small 1.5 x 3.2 mm, lead-free & halogen-free (ECOPACK2® ) 8-pin ceramic leadless chip carrier with embedded 32 KHz crystal - no external oscillator components required (M41T62)


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DS3840 DS3840: Low-power serial real-time clocks (RTCs) with alarm 22.0 920 KB
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Clocks and Timers Software


型号 Package Packing Type Operating Temperature (°C) (min) Operating Temperature (°C) (max) Marketing Status Unit Price (US$) * Quantity NVRAM size (B) ECCN (EU) ECCN (US) Country of Origin More info Order from ST Order from Distributors
M41T62LC6F LCC8 3.2x1.5 mm Tape And Reel -40 85 Active - - - NEC EAR99 - MORE INFO 获取样片 Add to cart DISTRIBUTOR AVAILABILITY
M41T62Q6F VFQFPN 16 3x3x0.9 Tape And Reel -40 85 Active - - - NEC EAR99 MALAYSIA MORE INFO 获取样片 Add to cart DISTRIBUTOR AVAILABILITY

(*) 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


型号 Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
M41T62LC6F ActiveLCC8 3.2x1.5 mmIndustrialEcopack2 0 0
M41T62Q6F ActiveVFQFPN 16 3x3x0.9IndustrialEcopack2 0 0

(**) 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.