The Cypress FM24VN10-G is a 1 Mbit Ferroelectric RAM (FRAM) in an 8-pin SOIC package, organized as 128K x 8 bits. It uses an I²C serial interface running at up to 3.4 MHz and offers a 130 ns access time. FRAM combines non-volatile storage with SRAM-like read/write speed and endurance — no battery backup, no wear-leveling needed. This part is meant for industrial data logging, metering, and configuration storage where the system writes frequently and needs data retention without a battery.
130 ns access — timing margin on the I²C bus
At 3.4 MHz (the high-speed I²C mode), the bit time is about 294 ns, so the FRAM has roughly half a bit period to respond. That is tight but within spec — the part is designed for this speed. If your master runs at 400 kHz standard mode, the margin is generous and the part works without any wait-state insertion.
The supply range is 2.0 V to 3.6 V, which covers both 3.3 V and 2.5 V rails. At 3.3 V the I²C bus levels are compatible with standard 3.3 V logic — no level shifter needed if the master is also 3.3 V. At 2.5 V the bus voltage is lower, so check the master's VIL/VIH thresholds.
That means Cypress (now Infineon) no longer produces it, and the only supply channel is the surplus / independent distribution market.
Replacement options — what fits the socket
If you need a drop-in replacement in the same 8-pin SOIC footprint with the same I²C interface, the closest functional sibling is the FM24V02A-G (256 Kbit, same 130 ns access, same 3.4 MHz I²C, same supply range and temperature grade). It is a lower-density part — 256 Kbit instead of 1 Mbit — so it only fits if your firmware fits in 32K x 8.