4Kbit SPI EEPROM for configuration and calibration storage
The Microchip AT25040B-SSHL-T is a 4Kbit serial EEPROM organized as 512 x 8 bits, accessed over an SPI bus at up to 20 MHz. It stores non-volatile data such as calibration coefficients, serial numbers, or configuration tables in systems that need to retain settings through power cycles.
SPI bus timing and write-cycle budget
The 20 MHz SPI clock delivers a read throughput of 2.5 MB/s in burst mode, fast enough to shadow the EEPROM contents into RAM at boot without stalling the host controller. Write-cycle time is 5 ms per word or page, so a full 512-byte rewrite takes roughly 40 ms if written page by page. For applications that log data or update parameters in the field, that write latency needs to fit within the system's non-critical timing window.
The -SSHL suffix indicates the narrow SOIC package; the -T suffix denotes Tape & Reel or Cut Tape shipping. The surface-mount package reflows with standard lead-free profiles, and the ROHS3 compliance means no substance restrictions for EU markets.
For dual-sourcing or a drop-in lower-density option, the AT25020B-SSHL-T (2Kbit, same package and pinout) is a functional second source — same SPI interface, same 20 MHz clock, same 1.8V–5.5V supply, same 8-SOIC footprint. The 4Kbit density here gives you twice the storage for the same board area.