What this FRAM does on the board
The Cypress FM25L16B-DG is a 16Kbit Ferroelectric RAM (FRAM) non-volatile memory organized as 2K x 8, accessed through a 20 MHz SPI interface. The part comes in an 8-DFN exposed-pad surface-mount package (4x4.5 mm).
20 MHz SPI and no write delays
The 20 MHz SPI clock is the bus speed limit; FRAM writes complete in a single SPI cycle with no page-write or erase overhead. For a design that logs sensor data every 10 ms, this eliminates the 5 ms EEPROM page-write penalty that can stall the bus. The 2.7 V minimum supply means the part stays alive through a 3.3 V rail droop to 2.7 V, which is useful in battery-backed or capacitor-hold scenarios.
For dual-sourcing resilience, the FM25L16B-G is a pin-compatible sibling in a different package variant (SOIC-8); confirm the footprint before substituting.