M41T256YMT7F

Real Time Clock Overview

The M41T256YMT7F is a low-power serial real-time clock (RTC) and static CMOS SRAM organized as 32K words by 8 bits. It features a built-in 32.768 kHz oscillator controlled by an external crystal, with 8 bytes of SRAM allocated for clock/calendar functions in BCD format. The device supports extended I2C bus addressing at 400 kHz and includes automatic power-fail detection with switchover to a backup battery supply. Key specifications include a 4.5 V to 5.5 V operating voltage range, a power-fail deselect voltage (VPFD) between 4.2 V and 4.5 V, and operation within a temperature range of -25°C to +70°C.

Real Time Clock Feature Summary

• Serial interface supporting extended I2C bus addressing at 400 kHz
• Automatic switch-over and deselect circuitry for power failures
• Tamper indication circuit with time-stamp capability
• Sleep mode function to minimize battery current draw during storage

Real Time Clock Applications

• Non-volatile timekeeping in systems requiring precise calendar tracking
• Data logging applications utilizing the 32,752 bytes of general-purpose RAM
• Security-sensitive devices requiring tamper detection and timestamping

Real Time Clock Procurement Notes

Verify that the specific ordering suffix MT7F corresponds to the 44-lead hatless SOIC package configuration. Confirm compatibility with external crystals and lithium button-cell batteries required for the SNAPHAT housing or direct connection. Ensure the design accounts for the separate shipping of the SNAPHAT top if using the integrated battery/crystal variant.

Real Time Clock Selection Notes

Select this component when high-density non-volatile memory (32KB) is required alongside RTC functionality. The 44-pin SOIC package allows for direct connection to a SNAPHAT top containing the battery and crystal, simplifying assembly by allowing post-reflow insertion. Ensure the system operates within the 4.5 V to 5.5 V voltage range and requires I2C communication capabilities.

Real Time Clock Part Context

The M41T256Y belongs to STMicroelectronics' TIMEKEEPER® series of serial RTCs. The 'MT' suffix denotes the 44-lead plastic small outline 'hatless' package, which provides sockets for connecting a separate SNAPHAT housing. This packaging strategy protects the battery and crystal from reflow soldering temperatures.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.