STMicroelectronics M41T11M6E

Overview

M41T11M6E from STMicroelectronics is a serial real-time clock (RTC) IC with integrated 32.768 kHz crystal oscillator, 56 bytes of NVRAM, I²C interface (100 kHz), ultra-low battery current (0.8 μA typ. at 3 V), and automatic power switchover - used for timekeeping and data retention in industrial control panels, point-of-sale terminals, and network infrastructure equipment.

For engineers reviewing the M41T11M6E datasheet, M41T11M6E pinout, M41T11M6E application, or M41T11M6E equivalent, key selection criteria include I²C timing compliance (tLOW ≥ 4.7 µs, tHIGH ≥ 4 µs), battery-backed operation down to 2.0 V, software-calibratable oscillator accuracy (±2 ppm after calibration), and SNAPHAT®-compatible 28-pin SOIC packaging with external battery/crystal housing support.

Technical Context

The M41T11M6E operates as an I²C slave device with fixed 7-bit address 0xD0h, supporting sequential read/write access across 64 bytes (8 clock/calendar registers + 56 NVRAM bytes). Its internal address pointer auto-increments on each acknowledged byte transfer, enabling burst-mode operations without repeated address writes.

It integrates a voltage-sense circuit that detects VCC falling below VSO (~2.0 V) and triggers automatic switchover to VBAT, disabling serial bus inputs and entering ultra-low-power retention mode. The oscillator uses internal 12.5 pF load capacitance and supports crystal series resistance up to 70 kΩ for stable startup across temperature (–40 to 85°C).

Key Specifications

Pinout & Package

Package: 28-lead plastic small outline (SOH28), 330 mil body width, with gold-plated dual-contact sockets for top-mounted SNAPHAT® battery/crystal housing (M4Txx-BR12SH). Compatible with surface-mount reflow; SNAPHAT installed post-reflow to avoid thermal damage.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231M and PCF8563, the M41T11M6E uniquely balances calibrated accuracy, SNAPHAT®-enabled modularity, and ultra-low battery drain - making it optimal for industrial systems needing field-replaceable timekeeping with minimal design overhead.

Availability

M41T11M6E is available at Aetrix Electronics and suitable for industrial automation, smart metering, and telecom infrastructure requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for M41T11M6E 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 sensor solutions for industrial, automotive, and consumer markets.

The M41T11 belongs to ST's real-time clock product line, engineered specifically for high-reliability, battery-backed timekeeping in harsh environments where long-term accuracy, data integrity, and thermal resilience are mandatory.

FAQ

What is the function of the FT/OUT pin on the M41T11M6E?

The FT/OUT pin is an open-drain output that can be configured to provide either a 1 Hz square wave or the raw 32.768 kHz oscillator signal. It is driven by internal clock dividers and requires an external pull-up resistor. This pin serves as a system timing reference or enables simple LED blinking without MCU intervention - its state is unaffected by I²C bus activity or power switchover events.

Does the M41T11M6E require external load capacitors for the crystal?

No. The M41T11M6E integrates 12.5 pF load capacitance internally on both OSCI and OSCO pins, eliminating the need for external ceramic capacitors. This simplifies PCB layout, reduces component count, and improves oscillator stability across temperature and board parasitics - confirmed by ST's characterization data showing reliable startup with crystal series resistance up to 70 kΩ.

How does the M41T11M6E handle leap years and century rollovers?

The M41T11M6E implements hardware-based leap year compensation using dedicated CE (Century Enable) and CB (Century Bit) flags in the hours register. When CE is set, the CB toggles automatically at year 2000/2100 boundaries, and the calendar logic correctly advances February 28 → 29 → March 1 in leap years. This occurs independently of host firmware, ensuring accurate date progression across decades without software updates.

Can the M41T11M6E operate solely on battery power without VCC applied?

Yes. When VCC is absent or below VSO (~2.0 V), the M41T11M6E automatically switches to VBAT and enters data retention mode, sustaining RTC counting and NVRAM contents with only 0.8 μA typical current draw. In this state, the I²C interface is disabled and the device ignores SDA/SCL activity - ensuring no spurious writes or register corruption during extended battery-only operation.