STMicroelectronics M41T00SM6E

Overview

M41T00SM6E from STMicroelectronics is a serial real-time clock (RTC) IC with integrated 32.768 kHz oscillator circuitry, designed for accurate timekeeping in battery-backed systems. It features BCD-formatted calendar registers (seconds to century), software-controlled clock calibration (±2 ppm achievable), automatic VCC-to-battery switchover at VSO = 2.5 V, and I²C-compatible 400 kHz serial interface. Used in industrial control panels requiring long-term timestamping under intermittent main power.

For engineers reviewing the M41T00SM6E datasheet, M41T00SM6E pinout, M41T00SM6E application, or M41T00SM6E equivalent, key selection criteria include ultra-low 0.6 µA battery current, built-in oscillator fail detection, automatic leap-year correction through year 2100, and seamless I²C bus integration without external level-shifting.

Technical Context

The M41T00SM6E operates as an I²C slave device with fixed 7-bit address 0xD0h, supporting sequential READ/WRITE access to eight internal registers. Its BiPORT™ TIMEKEEPER architecture maintains synchronized internal/external register copies to prevent read-modify-write corruption during clock updates.

Calibration is implemented via five programmable bits (D4–D0) in register 07h, enabling ±31-step adjustment at the 256-divider stage; sign bit D5 determines whether counts are added (positive) or subtracted (negative), with correction applied across a 64-minute cycle.

Key Specifications

Pinout & Package

Supplied in an 8-pin SOIC (SO8) package with 150-mil body width and standard gull-wing lead form factor, suitable for automated SMT assembly and IPC-compliant reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1307+, M41T00SM6E delivers 10× better calibrated accuracy and built-in fault detection; versus PCF8563, it trades 0.35 µA lower battery current for century support and active calibration-critical for infrastructure with >15-year service life.

Availability

M41T00SM6E 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 extended product lifecycles.

Supply support for M41T00SM6E 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, delivering microcontrollers, analog ICs, and timing solutions for industrial, automotive, and consumer markets.

The M41T00SM6E belongs to ST's TIMEKEEPER® RTC product line, engineered specifically for high-reliability, battery-backed timekeeping in industrial and medical equipment where calendar integrity and long-term accuracy are non-negotiable.

FAQ

Does M41T00SM6E require an external crystal?

Yes, the M41T00SM6E requires a standard 32.768 kHz tuning-fork crystal connected between XI and XO pins. The device integrates load capacitors (~12.5 pF each), eliminating need for external caps in most designs. Crystal tolerance directly impacts base accuracy before calibration.

How does the century bit (CB) function in register 02h?

The century bit (CB) resides in bit D7 of register 02h and toggles automatically at year rollover (1999→2000, 2099→2100) only when the century enable bit (CEB, also in D7) is set to '1'. CEB=0 locks CB, preventing unintended century transitions during firmware initialization or debugging.

What happens during I²C communication when VCC drops below VPFD?

When VCC falls below VPFD = 2.7 V, the M41T00SM6E terminates any ongoing I²C transaction, resets its internal address counter, and ignores further SDA/SCL activity until VCC rises above VPFD. This prevents corrupted register writes during brownout conditions.

Can FT/OUT pin be used as a general-purpose open-drain output?

Yes, the FT/OUT pin can be configured as a general-purpose open-drain output by clearing the FT bit (D6) in register 02h. In this mode, it functions as a controllable logic-level signal (active-low) independent of oscillator output, useful for status indication or interrupt signaling.