STMicroelectronics M41T00M6E

Overview

M41T00M6E from STMicroelectronics is a serial real-time clock (RTC) IC with integrated 32.768 kHz crystal oscillator, I²C interface (100 kHz), ultra-low battery current (0.8 μA typ at 3 V), and full BCD calendar registers (seconds to century). It provides automatic power switchover between V_CC and V_BAT, software calibration for temperature-induced crystal drift, and leap-year compensation - deployed in industrial control panels requiring long-term timekeeping during AC mains loss.

For engineers reviewing the M41T00M6E datasheet, M41T00M6E pinout, M41T00M6E application, or M41T00M6E equivalent, key selection criteria include battery-retained time accuracy across –40 to 85 °C, I²C timing compliance (t_SU:DAT = 250 ns, t_HD:DAT = 0 ns), switchover voltage threshold (V_SO = V_BAT − 0.50 V), and SO8 package compatibility with legacy board layouts.

Technical Context

The M41T00M6E operates as an I²C slave device with fixed 7-bit address 0xD0h, supporting sequential READ/WRITE of eight BCD-formatted registers (seconds through control). Its internal oscillator integrates 12.5 pF load capacitance and tolerates high-series-resistance crystals, enabling stable timekeeping without external capacitors.

Power management includes automatic V_CC-to-V_BAT switchover at V_SO = V_BAT − 0.50 V (typ), ultra-low retention current (0.8 μA), and 250 ms clock-update hold during register reads to prevent read-modify-write corruption. Calibration uses a 5-bit signed value (±0 to ±31) applied every 64 minutes to adjust the 32.768 kHz divider at the /256 stage.

Key Specifications

Pinout & Package

Supplied in an 8-lead plastic small outline (SO8) package, 150 mils body width, with gull-wing leads and standard JEDEC MS-012AC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1307+, the M41T00M6E delivers superior accuracy and reduced BOM count via integrated oscillator tuning; versus M41T00S, it trades minor power and ESD improvements for full backward compatibility with existing SO8 footprints and qualification data.

Availability

M41T00M6E is available at Aetrix Electronics and suitable for industrial control panels, smart utility meters, medical infusion pumps, and building automation controllers requiring stable component supply with guaranteed long-term availability.

Supply support for M41T00M6E 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, MCU, power, and timing solutions for industrial, automotive, and consumer markets.

The M41T00 series belongs to ST's precision timing product line, engineered specifically for battery-backed real-time clock applications where long-term accuracy, low power, and integration of oscillator components are critical design requirements.

FAQ

What is the function of the FT/OUT pin on the M41T00M6E?

The FT/OUT pin serves as a configurable open-drain output that can be programmed to deliver either a 1 Hz square wave or the raw 32.768 kHz oscillator signal. It is commonly used to drive LED blink indicators, synchronize external logic, or provide a test point for frequency verification during production calibration. Its open-drain structure allows direct connection to shared interrupt lines without contention.

How does the M41T00M6E handle leap years and month-end date rollovers?

The M41T00M6E implements fully autonomous BCD calendar logic that automatically increments day, date, month, year, and century registers - including February 29 insertion during leap years. This behavior is hardwired into the silicon and requires no firmware intervention. The device correctly handles all Gregorian calendar rules, such as skipping leap years in century years not divisible by 400.

Can the M41T00M6E operate without an external crystal?

No - the M41T00M6E requires an external 32.768 kHz tuning-fork crystal connected between OSCI and OSCO pins. While it integrates 12.5 pF load capacitance, the crystal itself is mandatory for oscillator functionality. Omitting the crystal results in no clock output, halted timekeeping, and zero current draw from V_BAT except leakage.

What happens during the V_CC to V_BAT switchover event?

When V_CC falls below the switchover threshold V_SO (V_BAT − 0.50 V), the M41T00M6E immediately terminates any ongoing I²C transaction, disables the SDA/SCL interface, and powers down non-essential circuitry. The oscillator and calendar registers remain fully active on V_BAT, preserving time and data with only 0.8 μA current draw. No reset or reinitialization is needed upon V_CC recovery.