STMicroelectronics M41T0DS6F

Overview

M41T0DS6F from STMicroelectronics is a serial real-time clock (RTC) 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 only 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 timekeeping - e.g., industrial HMIs, smart meters, and battery-backed data loggers.

For engineers reviewing the M41T0DS6F datasheet, M41T0DS6F pinout, M41T0DS6F application, or M41T0DS6F equivalent, key selection criteria include oscillator stability with internal 12.5 pF load capacitance, oscillator stop detection flag (OF bit), open-drain OUT pin programmability, I²C timing compliance (tLOW ≥1.3 µs, tHIGH ≥600 ns), and BCD register mapping for calendar functions.

Technical Context

The M41T0DS6F 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 under high-series-resistance crystal conditions. Its I²C slave interface uses fixed 7-bit address 0xD0h and supports sequential read/write of eight BCD registers (seconds to control).

Internal logic includes automatic address pointer incrementing, oscillator stop detection (OF bit set on power-up or crystal failure), and 250 ms clock-update hold during register reads to prevent mid-read corruption. The OUT pin mirrors bit D7 of the control register and requires external pull-up due to open-drain configuration.

Key Specifications

Pinout & Package

Package: SO8 (8-lead plastic small outline, 150 mils body width), 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 M41T0DS6F uniquely combines oscillator stop detection, integrated 12.5 pF load capacitance, and century-aware BCD registers - making it optimal for industrial applications demanding verifiable time integrity, reduced component count, and long-term calendar correctness.

Availability

M41T0DS6F is available at Aetrix Electronics and suitable for industrial data loggers, smart energy meters, human-machine interfaces, and factory automation controllers requiring stable component supply across extended product lifecycles.

Supply support for M41T0DS6F 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The M41T0DS6F belongs to ST's real-time clock product line, engineered specifically for robust, low-power timekeeping in harsh industrial environments - emphasizing oscillator reliability, I²C interoperability, and long-term calendar accuracy without external support components.

FAQ

What is the function of the NF pin on M41T0DS6F?

The NF (No Function) pin is an unused terminal that must be externally tied to VSS (ground) per the datasheet. It has no internal connection and serves no electrical purpose. Leaving it floating or connecting it to any voltage other than ground violates the device's recommended operating conditions and may cause undefined behavior or reduced reliability.

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

Upon initial power application, the OF (oscillator fail) bit is set to '1' by default, indicating undetermined oscillator status. It remains '1' until firmware explicitly clears it to '0' - but only after confirming the oscillator has run continuously for at least 4 seconds. This ensures time data is validated before being trusted in applications like billing or regulatory logging.

Can M41T0DS6F operate without an external crystal?

No. The M41T0DS6F requires an external 32.768 kHz tuning-fork crystal connected between OSCI and OSCO pins. Its internal oscillator circuit provides 12.5 pF load capacitance but no resonant element - removing the crystal halts timekeeping and sets the OF bit. No internal RC oscillator or alternative timebase is provided.

What is the significance of the century enable bit (CEB) in register 2?

The CEB (century enable bit) in the hours register controls automatic toggling of the century bit (CB) at year 2000/2100 boundaries. When CEB = 1, CB flips on century rollover (e.g., 1999→2000); when CEB = 0, CB remains static. This enables unambiguous year representation across centuries in BCD format - essential for long-lifecycle industrial equipment deployed beyond 2099.