STMicroelectronics M41T0M6F

Overview

M41T0M6F from STMicroelectronics is a serial real-time clock IC with integrated 32.768 kHz crystal oscillator, I²C interface (400 kHz), and BCD-formatted timekeeping registers for seconds through century. It operates from 2.0–5.5 V, draws 0.9 µA standby current at 3 V, and supports –40 to 85 °C industrial temperature range. Used in embedded systems requiring accurate, low-power time stamping and calendar functions.

For engineers reviewing the M41T0M6F datasheet, M41T0M6F pinout, M41T0M6F application, or M41T0M6F equivalent, key selection criteria include oscillator stability with internal 12.5 pF load capacitance, oscillator stop detection flag, open-drain OUT pin programmability, I²C timing compliance, and BCD register mapping for legacy firmware compatibility.

Technical Context

The M41T0M6F implements a fully autonomous RTC core driven by an external 32.768 kHz quartz crystal, with on-die oscillator circuitry integrating 12.5 pF load capacitance for stable oscillation even with high-series-resistance crystals. Its I²C slave interface uses fixed address 0xD0h and supports sequential read/write of eight BCD registers without manual address incrementing.

It features hardware-level oscillator fail (OF) detection that latches upon power-up or oscillation loss, and a STOP bit (ST) that halts the oscillator to reduce shelf current. The open-drain OUT pin reflects D7 of the control register and requires external pull-up; no internal driver is present.

Key Specifications

Pinout & Package

Supplied in SO8 (8-lead plastic small outline, 150 mils body width) package per JEDEC MS-012AC, with standard gull-wing lead form and 1.27 mm pitch.

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 M41T0M6F uniquely combines oscillator stop detection, integrated crystal load capacitance, and century bit support-making it optimal for applications requiring long-term time validity assurance and seamless Y2K+ date handling without firmware workarounds.

Availability

M41T0M6F is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, POS terminals, and medical infusion pumps requiring stable component supply across extended product lifecycles.

Supply support for M41T0M6F 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, MEMS, and power management solutions for industrial, automotive, and consumer markets.

The M41T0M6F belongs to ST's real-time clock product line, engineered specifically for low-power, high-reliability timekeeping in resource-constrained embedded systems where BCD register compatibility and oscillator health monitoring are critical.

FAQ

What is the function of the NF pin on the M41T0M6F?

The NF (No Function) pin is electrically unconnected and serves no internal purpose. Per the datasheet, it must be tied to VSS (ground) to ensure proper device operation and avoid floating node effects. It does not participate in I²C communication, oscillator function, or power distribution.

How does the oscillator stop detection (OF bit) behave during power-up?

On initial power application, the OF bit is set to '1' by default, indicating undetermined oscillator status. It remains '1' until firmware explicitly clears it-only after confirming the oscillator has run continuously for ≥4 seconds. This prevents false assumptions about time validity during boot.

Can the M41T0M6F operate without an external crystal?

No. The M41T0M6F requires an external 32.768 kHz tuning-fork crystal connected between OSCI and OSCO pins. Its internal oscillator circuit provides gain and 12.5 pF load capacitance but cannot function as a standalone clock source without the crystal resonator.

Is the OUT pin actively driven or open-drain?

The OUT pin is strictly open-drain. It can only sink current (pull low) when D7 of the control register is '0'; it cannot source current or drive high. An external pull-up resistor to VCC is mandatory to generate a valid logic-high level or drive external loads such as LEDs or interrupt lines.