The FM25640B-G2TR is a 64Kbit ferroelectric RAM organized as 8K x 8 bits, accessed over an SPI bus running up to 20 MHz. The FRAM cell writes without a page-erase cycle — each byte is written at bus speed, so the effective write throughput is limited by the SPI clock, not by the memory's internal timing. For a data logger logging 64-byte packets at 20 MHz, the write completes in roughly 30 µs, compared to several milliseconds for a serial EEPROM of the same density.
Obsolete — sourcing through surplus and broker channels
A pin-compatible alternative from the same family is not listed; any replacement would require a board spin or a parametric search across the 8-SOIC SPI FRAM class.
Surface-mount in an 8-SOIC package (3.90 mm body width, 0.154" pitch). The footprint matches industry-standard SOIC-8 land patterns used by serial memories and EEPROMs. No exposed pad — standard reflow profile for lead-free solder applies.