STMicroelectronics M41T82RM6E

Overview

M41T82RM6E from STMicroelectronics is an I²C real-time clock (RTC) IC in 8-lead SOIC package, providing battery-backed timekeeping with automatic VCC-to-VBAT switchover, ±5 ppm factory-calibrated accuracy (SOX18), ultra-low 365 nA battery supply current, and full BCD calendar registers (century, year, month, date, day, hour, minute, second, tenths/hundredths). It serves as a primary time-of-day source in industrial control panels requiring long-term timestamp integrity during main power loss.

For engineers reviewing the M41T82RM6E datasheet, M41T82RM6E pinout, M41T82RM6E application, or M41T82RM6E equivalent, this page delivers verified technical context, validated pin functions, confirmed RTC calibration architecture, and real-world use cases for embedded systems requiring fail-safe timekeeping under intermittent power.

Technical Context

The M41T82RM6E implements a crystal-controlled 32.768 kHz oscillator with XI/XO pins, internal power-sense circuitry triggering seamless switchover to VBAT at fixed VRST = 2.93 V (S-grade), and a dedicated open-drain FT/RST pin combining frequency test output and power-on reset signaling. Its I²C interface operates at up to 400 kHz with standard 7-bit slave address 0xD0h.

It features dual alarm capability (Alarm 1 interrupt active in battery backup mode), oscillator stop detection, battery low flag, and 7 bytes of battery-backed SRAM - all managed via a 32-byte register map accessed sequentially after start condition and address byte. The device lacks square wave output and IRQ2, distinguishing it from M41T83 variants.

Key Specifications

Pinout & Package

Package: 8-lead SOIC (4.90 mm × 3.90 mm), RoHS-compliant, surface-mount.

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 M41T82RM6E uniquely combines factory-trimmed ±5 ppm accuracy, alarm persistence in battery mode, and hardware oscillator failure detection - making it optimal for industrial and medical applications demanding certified time integrity.

Availability

M41T82RM6E is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, PLC control panels, and medical diagnostic devices requiring stable component supply across extended product lifecycles.

Supply support for M41T82RM6E 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, and power management solutions for industrial, automotive, and consumer markets.

The M41T82RM6E belongs to ST's precision timing product line, engineered specifically for battery-backed real-time clock applications where long-term accuracy, low power, and robust power-fail response are non-negotiable design requirements.

FAQ

What is the function of the FT/RST pin on M41T82RM6E?

The FT/RST pin serves two distinct roles: it outputs a power-on reset pulse (open-drain, active-low) upon VCC ramp-up, and provides a 32.768 kHz frequency test signal when enabled via register control. Unlike M41T83 variants, it does not support IRQ1 or SQW functions - its dual-mode behavior is hardwired and requires no external components.

Does M41T82RM6E support automatic leap-year correction?

Yes. The M41T82RM6E's BCD calendar registers automatically adjust for February lengths in leap years (e.g., 29 days in 2024) and non-leap years (28 days in 2023), as well as variable month lengths (30 vs. 31 days). This correction is implemented in hardware and requires no firmware intervention - all date arithmetic is handled internally.

Can the M41T82RM6E operate without an external crystal?

No. The M41T82RM6E requires an external 32.768 kHz tuning-fork crystal connected between XI and XO pins. It does not include an embedded crystal (unlike M41T83 SOX18 variants). The oscillator circuit is designed for 12.5 pF load capacitance; deviation beyond ±2 pF degrades accuracy and may cause startup failure.

How is battery switchover triggered, and what happens to the RTC during transition?

Switchover activates when VCC falls below the fixed VRST threshold of 2.93 V (S-grade). The internal power-sense circuit immediately disconnects VCC and connects VBAT to the RTC core - timekeeping continues uninterrupted with zero clock cycle loss. All registers, alarms, and SRAM retain state; no reset or reinitialization occurs.