STMicroelectronics M41T94MH6E

Overview

M41T94MH6E from STMicroelectronics is a serial real-time clock (RTC) IC with integrated 32.768 kHz oscillator, 44 bytes of non-volatile RAM (NVRAM), programmable alarm, watchdog timer, and RESET output. It operates from 2.7–5.5 V, consumes ≤500 nA in battery backup mode, and supports SPI up to 2 MHz. Used in industrial control panels for accurate time-stamping of event logs during mains power loss.

For engineers reviewing the M41T94MH6E datasheet, M41T94MH6E pinout, M41T94MH6E application, or M41T94MH6E equivalent, key selection criteria include battery-backed timekeeping integrity, SPI timing compatibility (CPOL/CPHA = '0','0' or '1','1'), low-V_CC switchover thresholds (2.55–2.70 V or 4.20–4.50 V), and SNAPHAT®-integrated 28-pin SOIC package support.

Technical Context

The M41T94MH6E implements a BCD-encoded RTC core with automatic leap-year correction through year 2100 and century-bit handling. Its oscillator integrates 12.5 pF load capacitance, enabling stable operation with high-series-resistance crystals - critical for long-term reliability in temperature-variable environments.

It functions as an SPI slave with dual reset inputs (RSTIN1/RSTIN2), open-drain IRQ/FT/OUT and RST outputs, and hardware-controlled power-fail detection that triggers automatic V_CC-to-battery switchover within t_REC (recovery time) before write protection engages.

Key Specifications

Pinout & Package

Package: SOH28 - 28-lead plastic small outline, 330 mil width, RoHS-compliant, lead-free second-level interconnect. Designed for direct mating with ST's SNAPHAT® housing (e.g., M4TXX-BR12SH) containing integrated lithium battery and 32.768 kHz crystal.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3231SN#T&R and PCF8563T, the M41T94MH6E uniquely combines SPI interface, SNAPHAT®-ready 28-pin SOIC packaging, dual reset inputs, and selectable V_PFD thresholds - making it optimal for industrial designs requiring robust, drop-in timekeeping with minimal layout overhead.

Availability

M41T94MH6E is available at Aetrix Electronics and suitable for industrial HMI logging, medical device time stamping, and smart energy metering requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for M41T94MH6E 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 microcontrollers, analog ICs, power management devices, and sensors for industrial, automotive, and consumer markets.

The M41T94 belongs to ST's real-time clock product line, engineered specifically for industrial and medical systems demanding reliable, battery-backed timekeeping with integrated power-fail management and minimal external components.

FAQ

What is the function of the THS pin on the M41T94MH6E?

The THS (Threshold Select) pin configures the power-fail switchover reference voltage: when tied to V_SS, V_PFD is 2.55–2.70 V; when tied to V_CC, V_PFD is 4.20–4.50 V. This allows matching the device's brown-out response to system-level supply monitoring thresholds without external resistive dividers.

Can the M41T94MH6E operate without an external crystal?

No - the M41T94MH6E requires an external 32.768 kHz crystal connected between XI and XO pins. Its integrated 12.5 pF load capacitance eliminates the need for external load capacitors, but the crystal itself is mandatory for oscillator operation and RTC timekeeping.

How does the SNAPHAT® top integrate with the M41T94MH6E SOH28 package?

The SOH28 package features gold-plated sockets at both ends that mate directly with ST's 4-pin SNAPHAT® housing (e.g., M4TXX-BR12SH), which contains the lithium battery and crystal. The top is mounted post-reflow to avoid thermal damage, and its keyed design prevents reverse insertion - enabling true "plug-and-play" RTC assembly.

What is the purpose of the IRQ/FT/OUT pin?

The IRQ/FT/OUT pin is a multifunction open-drain output configurable as: (1) alarm interrupt signal, (2) frequency test point for SQW output verification, or (3) general-purpose output. Its state is controlled via register bits and remains functional during battery backup mode for critical wake-up signaling.