STMicroelectronics M41T56MH6F

Overview

M41T56MH6F from STMicroelectronics is a serial real-time clock (RTC) IC with integrated 56-byte NVRAM, I²C interface (100 kHz), ultra-low battery current (450 nA typ), and built-in 32.768 kHz crystal oscillator with 12.5 pF load capacitance. It performs full calendar/timekeeping (seconds to century), automatic leap-year compensation, and power-fail detection with seamless VCC-to-battery switchover - used in industrial control panels requiring long-term timestamping and data logging under intermittent power.

For engineers reviewing the M41T56MH6F datasheet, M41T56MH6F pinout, M41T56MH6F application, or M41T56MH6F equivalent, key selection criteria include battery-backed timekeeping down to 2.5 V, software-adjustable ±2 ppm calibration at 25 °C, I²C slave address 0xD0h, SO8 package compatibility, and guaranteed operation from –40 °C to +85 °C.

Technical Context

The M41T56MH6F implements a BCD-formatted 8-register clock/calendar (seconds through century) with automatic 250 ms register update delay during read access to prevent mid-read corruption. Its oscillator uses periodic counter correction - not external trim caps - applying ±31-step calibration via five bits (D4–D0) in the control register (address 7), where D5 serves as sign bit.

It operates as an I²C slave with fixed 7-bit address 0x68 (D0h write / D1h read), supports standard-mode timing (tLOW ≥ 4.7 µs, tHIGH ≥ 4 µs), and features autonomous power management: detects VCC drop below VPFD (~4.25 V), disables writes, then switches to VBAT when VCC falls below VSO (~2.5 V), entering <450 nA retention mode with all outputs high-impedance.

Key Specifications

Pinout & Package

Package: 8-lead plastic SOIC (SO8), 150-mil body width, RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RTC-with-NVRAM applications.

Compared with DS1337+T&R and PCF8563T, the M41T56MH6F uniquely integrates oscillator load capacitance and software calibration to achieve ±2 ppm accuracy without external components, while maintaining timekeeping down to 2.5 V - making it optimal for space-constrained, long-life industrial systems.

Availability

M41T56MH6F 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, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for M41T56MH6F 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, power management ICs, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M41T56MH6F belongs to ST's real-time clock product line, engineered specifically for battery-backed, high-accuracy timekeeping in resource-constrained embedded systems where reliability, low power, and calendar intelligence are critical.

FAQ

What is the I²C slave address of the M41T56MH6F?

The M41T56MH6F uses a fixed 7-bit I²C slave address of 0x68 (1011000b) for write operations and 0x69 for read operations. This corresponds to the documented address D0h (hex) in the datasheet, where the R/W bit is appended externally by the master. No address pins or configuration bits alter this value - it is hardwired in silicon.

Does the M41T56MH6F require external load capacitors for the 32.768 kHz crystal?

No. The M41T56MH6F integrates 12.5 pF load capacitance internally across the OSCI and OSCO pins, eliminating the need for external capacitors. This simplifies PCB layout, reduces BOM count, and improves oscillator start-up reliability - especially under temperature variation and board parasitic effects.

How does the M41T56MH6F handle leap years and century transitions?

The M41T56MH6F performs automatic leap-year calculation based on Gregorian calendar rules and includes a dedicated Century Enable Bit (CEB) in the hours register. When CEB = 1, the Century Bit (CB) toggles at year 2000/2100 boundaries; when CEB = 0, CB remains static - enabling deterministic Y2100 compliance without firmware intervention.

What happens to the RTC registers during a power failure?

When VCC drops below VPFD (~4.25 V), the M41T56MH6F immediately halts I²C access, resets its internal address pointer, and enters write-protected mode. At VCC < VSO (~2.5 V), it switches to VBAT, disables all outputs (high-Z), and sustains clock and RAM operation at <450 nA - preserving time and data without corruption.