STMicroelectronics M41T82SM6F

Overview

M41T82SM6F from STMicroelectronics is an I²C real-time clock (RTC) IC in 8-lead SOIC package, providing battery-backed timekeeping with ±5 ppm factory-calibrated accuracy, ultra-low 365 nA battery supply current, and automatic VCC-to-battery switchover at 2.93 V. It supports full BCD calendar (century, year, month, date, day, hour, minute, second, tenths/hundredths), programmable alarm interrupt, oscillator fail detection, and operates from –40 °C to +85 °C - used in industrial control panels requiring long-term timestamp integrity during main power loss.

For engineers reviewing the M41T82SM6F datasheet, M41T82SM6F pinout, M41T82SM6F application, or M41T82SM6F equivalent, this page delivers verified technical context, validated pin functions, confirmed RTC calibration architecture, and precise alternative selection guidance for time-critical embedded systems.

Technical Context

The M41T82SM6F implements a crystal-controlled 32.768 kHz oscillator with internal load capacitance tuning (analog calibration) and periodic counter correction (digital calibration), enabling post-reflow accuracy of ±5 ppm typical. Its I²C interface complies with 400 kHz Fast Mode timing, supporting sequential read/write across 32-byte register map including 8 clock/calendar bytes, 17 control/status bytes, and 7 bytes of battery-backed SRAM.

Power management includes dedicated FT/RST open-drain output for power-on reset assertion and frequency test mode, plus hardware-based battery switchover triggered when VCC falls below VRST = 2.93 V (S-grade). Oscillator stop detection and battery low flag are implemented as independent status bits readable via I²C.

Key Specifications

Pinout & Package

Package: SO8 (4.90 mm × 3.90 mm), RoHS-compliant, surface-mount plastic small outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1337+T&R and PCF8563T, the M41T82SM6F provides superior accuracy stability via dual calibration, robust fault detection for safety-critical use, and broader voltage tolerance - making it optimal for industrial systems demanding long-term reliability under thermal and supply stress.

Availability

M41T82SM6F is available at Aetrix Electronics and suitable for industrial data loggers, medical infusion pumps, smart energy meters, and building automation controllers requiring stable component supply across multi-year production cycles.

Supply support for M41T82SM6F 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, designing and manufacturing microcontrollers, power management ICs, sensors, and timing devices for industrial, automotive, and consumer markets.

The M41T82SM6F belongs to ST's serial RTC product line, engineered specifically for high-accuracy, low-power timekeeping in harsh environments where battery longevity and calibration resilience are mandatory.

FAQ

What is the function of the FT/RST pin on M41T82SM6F?

The FT/RST pin serves dual roles: as an open-drain power-on reset output that asserts low during VCC ramp-up (trec ≈ 250 ms), and as a frequency test output that mirrors the 32.768 kHz oscillator signal for validation. It does not support interrupt generation or square wave output - those functions are exclusive to M41T83 variants.

Does M41T82SM6F require external load capacitors for the crystal?

No. The M41T82SM6F integrates the oscillator feedback resistor and supports direct connection of a standard 32.768 kHz tuning-fork crystal between XI and XO pins without external load capacitors. This simplifies layout and improves EMI immunity compared to discrete oscillator implementations.

How is calendar data formatted in the M41T82SM6F register map?

Time and date values are stored in binary-coded decimal (BCD) format across eight consecutive registers: tenths/hundredths of seconds, seconds, minutes, century/hours, day, date, month, and year. Each byte contains two 4-bit BCD digits (e.g., 0x12 = 12 decimal), enabling direct human-readable interpretation without software conversion.

Can the M41T82SM6F operate without a battery connected?

Yes - VBAT may be tied to VSS if battery backup is not required. In that configuration, the RTC retains timekeeping only while VCC is present; all calendar and alarm functions cease during power loss. The device remains fully functional for main-supply-only applications such as short-duration portable instruments.