The 28-pin SOJ package (28-BSOJ, 0.400" body width) is a surface-mount footprint common in late-1990s through 2010s networking and telecom equipment. This part was designed for high-speed cache, buffer, or scratchpad memory in systems that need fast random access without the complexity of synchronous clocking.
For a legacy DSP or FPGA design that already has a 5 V supply rail and a parallel memory controller, this part fits directly into the timing budget without needing a PLL or DLL to deskew the data. The 10 ns write cycle time (word and page) matches the read access, so back-to-back read-write sequences run at full speed with no dead cycles.
Infineon (formerly Cypress) has discontinued production; there is no last-time-buy window remaining. Any units on the market are new-old-stock or surplus inventory.
Package and footprint — what the SOJ means on the board
The 28-SOJ package (JEDEC MO-119 variant, 0.400" body width, 10.16 mm) is a gull-wing lead form with a 1.27 mm pitch. It is a surface-mount part but the leads are on the outer edges — no thermal pad underneath. The Tube shipping medium (25 pieces per tube) is typical for this package; reels are available under alternate order codes.