64Kbit FRAM with SPI — what it replaces on the board
The Cypress FM25CL64B-DG is a 64Kbit non-volatile FRAM (Ferroelectric RAM) organized as 8K x 8 bits, accessed through an SPI interface running at up to 20 MHz. The 8-DFN (4x4.5 mm) package with exposed pad suits compact designs where serial EEPROM or battery-backed SRAM was previously used, but with the write endurance and speed of FRAM — no page writes, no erase cycles needed before a write.
The supply range of 2.7V to 3.6V covers the standard 3.3V rail with margin. At 3.3V nominal, the part operates within its specified window, and the SPI interface levels are compatible with 3.3V logic. If the system uses a 2.5V or 1.8V core, a level translator on the SPI lines would be needed — the FM25CL64B-DG does not support lower supply voltages.
20 MHz SPI — throughput for configuration data
The 20 MHz SPI clock rate delivers a read throughput of roughly 20 Mbps. For storing calibration constants or event logs, the FRAM's write speed means the SPI bus is the bottleneck, not the memory array.