STMicroelectronics M41T00SM6F

Overview

M41T00SM6F from STMicroelectronics is a low-power serial real-time clock (RTC) with integrated 32.768 kHz oscillator circuitry, designed for accurate timekeeping in battery-backed systems. It provides BCD-formatted century/year/month/date/day/hour/minute/second counters, supports I²C bus communication at 400 kHz, operates from 2.0–5.5 V, and delivers ultra-low battery current of 0.6 µA over –40 to +85 °C.

For engineers reviewing the M41T00SM6F datasheet, M41T00SM6F pinout, M41T00SM6F application, or M41T00SM6F equivalent, this device serves as a drop-in calendar/timekeeping solution requiring automatic leap-year correction, oscillator fail detection, software calibration, and seamless VCC-to-battery switchover in embedded control, industrial HMIs, and metering systems.

Technical Context

The M41T00SM6F functions as an I²C slave device with fixed 7-bit address 0xD0h, using a bidirectional SDA/SCL interface compliant with standard-mode (100 kHz) and fast-mode (400 kHz) timing. Its internal BiPORT™ TIMEKEEPER architecture maintains dual register copies - external (user-accessible) and internal (auto-updated) - to prevent read corruption during clock updates.

It implements a 64-minute calibration cycle where five programmable bits (D4–D0) plus sign bit (D5) in register 07h control ±31 count adjustments per minute at the divide-by-256 stage, enabling software tuning to better than ±2 ppm at 25 °C. Oscillator stop detection (ST bit in register 00h) and automatic switchover at VSO (2.5 V ≤ VPFD ≤ 2.7 V) ensure continuous timekeeping during power loss.

Key Specifications

Pinout & Package

Supplied in an 8-pin SOIC (SO8) package with 150-mil body width, surface-mount footprint, and JEDEC MS-012AC mechanical outline.

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 M41T00SM6F uniquely integrates oscillator, century-aware calendar, and ±2 ppm calibration in one SO8 package - reducing BOM count, eliminating crystal layout sensitivity, and enabling decade-long timestamp reliability without host intervention.

Availability

M41T00SM6F is available at Aetrix Electronics and suitable for smart metering, industrial HMI, medical infusion pumps, and building automation controllers requiring stable component supply, long-lifecycle support, and guaranteed traceability.

Supply support for M41T00SM6F 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 automotive, industrial, and power management solutions with strong analog and mixed-signal IP.

The M41T00SM6F belongs to ST's TIMEKEEPER® RTC product line, engineered specifically for high-reliability, battery-backed timekeeping in industrial and metering applications where calendar accuracy, low power, and long-term stability are non-negotiable.

FAQ

What is the function of the FT/OUT pin on the M41T00SM6F?

The FT/OUT pin serves dual roles: as an open-drain frequency test output delivering a calibrated 32.768 kHz square wave, and as a configurable output driver for user-defined signals. It requires an external pull-up resistor and reflects oscillator health via the OF (oscillator fail) bit in its status register. This pin enables real-time validation of crystal operation without external test equipment.

How does the M41T00SM6F handle leap years and variable month lengths?

The M41T00SM6F performs fully autonomous calendar correction in hardware: it automatically adjusts for 28-, 29- (leap year), 30-, and 31-day months using internal logic tied to the century/year registers. Leap-year calculation remains valid through year 2100, eliminating the need for host MCU intervention or date arithmetic in firmware.

Can the M41T00SM6F operate without an external crystal?

No - the M41T00SM6F requires an external 32.768 kHz tuning-fork crystal connected between XI and XO pins to generate its timebase. The device contains the oscillator circuitry (inverter, feedback resistor, load capacitors) but not the resonator itself. Omitting the crystal disables timekeeping entirely, though I²C communication remains functional for register access.

What happens during a power failure, and how quickly does switchover occur?

When VCC falls below the switchover threshold VSO (2.5–2.7 V), the M41T00SM6F immediately disconnects from VCC and activates VBAT within microseconds, preserving all clock registers and oscillator state. No time is lost, and no register corruption occurs. Upon VCC recovery above VPFD (2.5–2.7 V), write protection remains active for tREC (typically 100 ms) to prevent spurious writes during supply stabilization.