STMicroelectronics M41T80M6F

Overview

M41T80M6F from STMicroelectronics is a serial-access real-time clock (RTC) IC with integrated 32.768 kHz crystal oscillator, I²C interface (400 kHz), alarm interrupt capability, and programmable square-wave output (1 Hz to 32 kHz). It maintains time-of-day and calendar data-including century, leap-year-corrected date, and tenths/hundredths of seconds-in BCD format, and operates across –40 to +85 °C for industrial embedded timing applications.

For engineers reviewing the M41T80M6F datasheet, M41T80M6F pinout, M41T80M6F application, or M41T80M6F equivalent, this device serves as a low-power, self-contained RTC solution requiring no external load capacitors, supporting precise timekeeping in battery-backed systems, energy meters, and industrial controllers where deterministic alarm triggering and stable 32 kHz reference generation are critical.

Technical Context

The M41T80M6F implements a fully autonomous RTC core driven by an internal 32.768 kHz oscillator with integrated 12.5 pF load capacitance-enabling high stability and tolerance of elevated crystal series resistance. Its I²C slave interface uses fixed address 0xD0h and supports sequential read/write access across 20 registers, with automatic address pointer incrementation.

Clock registers (00h–07h) store time/date in BCD with hardware-assisted leap-year correction (valid through year 2100); alarm registers (0Ah–0Eh) support repeat modes from once-per-second to annual via RPT1–RPT5 bits; control logic includes STOP bit (ST) to halt oscillator and reduce standby current to <1 µA, and dedicated OUT/SQW open-drain pin configurable as IRQ, square wave, or 32 kHz output.

Key Specifications

Pinout & Package

Package: 8-pin SOIC (SO8), 150 mil body width, ECOPACK® RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock applications.

Compared with DS1307+ and PCF8563, the M41T80M6F uniquely combines integrated oscillator capacitance, century-aware calendar, and dual-output capability (IRQ + F32K) - making it optimal for industrial systems demanding long-term accuracy, minimal BOM count, and deterministic alarm behavior without firmware overhead.

Availability

M41T80M6F is available at Aetrix Electronics and suitable for smart metering, industrial HMI, medical infusion pumps, and building automation controllers requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for M41T80M6F includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The M41T80 belongs to ST's precision timing product line, engineered specifically for robust, low-power real-time clocking in harsh environments where reliability, long-term accuracy, and minimal external components are essential design requirements.

FAQ

What crystal specifications are required for the M41T80M6F?

The M41T80M6F requires a standard 32.768 kHz tuning-fork crystal with fundamental-mode operation, load capacitance of 12.5 pF (matched by internal oscillator), and series resistance ≤50 kΩ. ST recommends crystals with frequency tolerance ≤20 ppm and aging ≤5 ppm/year to maintain long-term accuracy within ±2 minutes/year over temperature.

How does the M41T80M6F handle leap years?

The M41T80M6F automatically corrects February length for leap years using hardware logic valid through year 2100. When the year register (07h) contains '00' and month (06h) is '02', the date register (05h) rolls from 28 to 29 on leap years - no firmware action is needed, and the century bit (CB) toggles correctly at year 2100 when CEB is enabled.

Can the IRQ/OUT/SQW pin be used simultaneously as interrupt and square-wave output?

No - IRQ/OUT/SQW is a single open-drain pin with three mutually exclusive functions selected via control register bits. It cannot output both interrupt pulses and square-wave signals concurrently. For simultaneous use, the dedicated F32K pin must be used for 32 kHz output while IRQ/OUT/SQW serves as alarm interrupt or programmable SQW.

Is the M41T80M6F compatible with 1.8 V I²C systems?

No - the M41T80M6F's I²C interface is specified for VCC = 2.0–5.5 V only. Its SDA/SCL pins are not 1.8 V tolerant, and the minimum high-level input voltage (VIH) is 0.7 × VCC. Interfacing with 1.8 V microcontrollers requires level-shifting circuitry or selection of a different RTC with native 1.8 V I²C support.