1.8 V NOR Flash — the supply-rail gate
The Infineon S25FS128SAGMFI100 is a 128 Mbit NOR Flash from the FS-S series, built for designs that run on a 1.7 V to 2 V supply rail. That supply range is the first thing to check against your board — it is a strict 1.8 V nominal part, not a 2.7 V or 3.3 V device. The 133 MHz clock rate matches the rest of the 128 Mbit FS-S and FL-S family, so if you are migrating from a sibling part at the same density, the speed grade is not a differentiator.
Sourcing and lifecycle — still a current-production line
It is RoHS3 compliant and ships in a tray, though production reels are common through distribution.
What the 1.8 V supply means for the BOM
Because the supply range tops out at 2 V, this part cannot be dropped onto a 2.5 V or 3.3 V bus without a level translator or a separate LDO. The SPI and Quad I/O signals must also stay within the same 1.8 V domain — mixing voltage levels on the bus risks latch-up or incorrect logic thresholds. If your system already has a 1.8 V rail for the core or I/O bank, this Flash fits without extra regulation. If you are running a 2.7 V or 3.3 V NOR elsewhere in the family (like the S25FL128L series), the supply change is the main barrier to a drop-in swap.