64Kbit serial EEPROM in a 4-bump WLCSP
The 4-bump WLCSP package (4-XFBGA) is the smallest footprint option in the M24C64 family, intended for space-constrained PCBs where a standard SOIC or TSSOP cannot fit.
Obsolete — plan for a replacement
The M24C64S-FCU6T/T is officially marked as Obsolete by STMicroelectronics. For new designs or sustained production, a replacement must be qualified. The base product number M24C64 covers multiple package variants; the WLCSP version is the one being phased out.
I²C bus timing and write cycle
The I²C interface runs at a 1 MHz clock frequency, supporting fast-mode plus data rates. Access time is 650 ns, which is the read cycle time from the last address. The write cycle time for a word or page is 5 ms — a standard figure for this density class. When budgeting firmware timing for page writes, account for the 5 ms non-acknowledging period after each write command.
Package and handling for the 4-WLCSP
This is a chip-scale package with no leads — the solder bumps are directly on the die. Surface-mount assembly requires a stencil designed for the bump pitch and a reflow profile compatible with the board's solder mask.