Small-configuration storage for field swaps
The Microchip 24LC025T-I/ST is a 2Kbit serial EEPROM with an I²C interface, organized as 256 x 8 bits. It stores calibration constants, serial numbers, or configuration tables that survive power loss — the kind of data you want to swap in the field without reprogramming the main MCU. The 8-TSSOP package (4.40 mm wide) is small enough to fit on a cramped control board and common enough that I keep a few in my field kit.
It is RoHS3 compliant, which clears the compliance gate for new designs shipping into Europe or California.
I²C interface and write-cycle timing
The I²C interface runs at 400 kHz, the standard fast-mode speed. Write-cycle time is 5 ms per word or page — typical for this density, so a 256-byte page write takes about 5 ms plus addressing overhead. That is fast enough for storing configuration at power-down but not for streaming data.