M41T81SMY6F

Real Time Clock Overview

The M41T81SMY6F is a low-power serial real-time clock (RTC) from STMicroelectronics, part of the M41T81S family. It features an I2C bus interface and operates within a supply voltage range of 2.0 V to 5.5 V. The device includes a built-in 32.768 kHz oscillator requiring an external crystal, with automatic switchover to battery backup upon power failure. It provides clock/calendar functions in BCD format, programmable alarms, watchdog timer, and square wave output. The component is housed in an 8-SOIC package and supports industrial operating temperatures from -40°C to +85°C.

Real Time Clock Feature Summary

• I2C bus interface supporting 400 kHz protocol
• Automatic power fail detection and battery switchover circuitry
• Built-in 32.768 kHz oscillator with oscillator stop detection
• Programmable alarm with interrupt function valid during battery backup

Real Time Clock Applications

• Smart grid distribution and smart meters
• Industrial control systems requiring precise timekeeping
• Consumer electronics with battery-backed memory requirements

Real Time Clock Procurement Notes

Verify the specific suffix 'M' against official ST documentation to confirm pinout and feature set differences compared to standard M41T81 variants. Confirm RoHS compliance status via the manufacturer's datasheet or environmental declaration. Check for moisture sensitivity level (MSL) ratings if lead-free soldering processes are required for assembly.

Real Time Clock Selection Notes

Select this component when an I2C-connected RTC with low standby current is needed. Ensure the system design accommodates an external 32.768 kHz crystal due to the SOIC package variant lacking an embedded crystal. Verify that the 2.0 V to 5.5 V operating voltage range aligns with the target system's power rails.

Real Time Clock Part Context

The M41T81SMY6F belongs to the M41T81S series of serial real-time clocks. This series is distinguished by its I2C compatibility and ultra-low power consumption. The 'SM' suffix typically denotes the SOIC-8 package configuration with an external crystal requirement, differentiating it from SOX18 variants which include an embedded crystal.

Real Time Clock Replacement Considerations

Direct pin-to-pin replacements within the same family include M41T81ST6F or M41T81WM6F, provided the package and electrical specifications match. Cross-family replacements require verification of I2C address compatibility and register map alignment.