STMicroelectronics M41T82ZM6E

Overview

M41T82ZM6E from STMicroelectronics is a serial 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), and ultra-low 365 nA battery supply current. It supports BCD-formatted calendar counters (century, year, month, date, day, hour, minute, second, tenths/hundredths), programmable alarm interrupt, watchdog timer, and 7-byte battery-backed SRAM - deployed in industrial control panels requiring long-term timestamp integrity during mains loss.

For engineers reviewing the M41T82ZM6E datasheet, M41T82ZM6E pinout, M41T82ZM6E application, or M41T82ZM6E equivalent, key selection criteria include its fixed FT/RST open-drain reset output, absence of SQW output (distinguishing it from M41T83 variants), SO8 footprint compatibility, and 2.0–5.5 V operating voltage range with battery low flag detection.

Technical Context

The M41T82ZM6E implements a dedicated I²C slave interface (7-bit address 0xD0) with automatic register pointer increment, supporting read/write sequences up to 32 bytes. Its internal 32.768 kHz oscillator requires external crystal connected between XI and XO pins, with oscillator stop detection and halt bit (HT) for power-down time-stamping.

Power management includes dual-threshold switchover (VSO = VRST = 2.32 V for Z-grade), built-in power-on reset (trec = 250 ms typ.), and write-protect logic activated when VCC drops below VRST. The FT/RST pin serves as both frequency test output and open-drain reset signal - a hardware-level system initialization resource not shared with interrupt or square wave functions.

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 DS1307+ and PCF8563, the M41T82ZM6E delivers superior accuracy stability, integrated power-fail resilience, and richer time-management peripherals - making it optimal for industrial systems where timestamp integrity and autonomous fault response are mandatory.

Availability

M41T82ZM6E is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, medical infusion pumps, and building automation controllers requiring stable component supply across multi-year production cycles.

Supply support for M41T82ZM6E 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, power management ICs, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M41T82ZM6E belongs to ST's precision RTC product line, engineered specifically for applications demanding high-accuracy, long-term timekeeping with robust power-fail handling and minimal external components - targeting industrial control, metering, and medical equipment.

FAQ

What is the function of the FT/RST pin on the M41T82ZM6E?

The FT/RST pin serves two distinct hardware roles: as an open-drain power-on reset signal (active-low, trec = 250 ms typical) and as a frequency test output (32.768 kHz square wave). It cannot generate alarm interrupts or square wave outputs - those functions are exclusive to M41T83 variants. The pin is internally tied to the reset generator and oscillator test circuitry, with no software-configurable mode selection.

Does the M41T82ZM6E support automatic leap-year correction?

Yes. The M41T82ZM6E's BCD-formatted calendar registers (century, year, month, date) implement hardware-level leap-year logic that automatically adjusts February length for years divisible by 4, excluding century years not divisible by 400. This correction operates independently of host MCU intervention and remains functional during battery backup mode.

Can the M41T82ZM6E operate without an external crystal?

No. The M41T82ZM6E requires an external 32.768 kHz tuning-fork crystal connected between XI and XO pins to sustain oscillation. Unlike the SOX18-packaged M41T83, it contains no embedded crystal. Omitting the crystal results in oscillator stop detection, halted timekeeping, and assertion of the oscillator fail flag - with no fallback timing source.

How is battery switchover threshold determined for the Z-grade variant?

The Z-grade M41T82ZM6E uses a fixed internal switchover threshold of 2.32 V (VSO = VRST), verified per ST's DocID012578 Rev 19. This value is laser-trimmed during final test and is not user-adjustable. Switchover occurs within 1 µs of VCC crossing 2.32 V downward, ensuring no clock cycle is lost during transition to VBAT power.