128K x 9 synchronous FIFO — timing and capacity for buffering
The CY7C4291-10JXC is a synchronous FIFO memory from the CY7C series, organized as 128K words by 9 bits (1.125 Mbit total capacity). It clocks at 100 MHz with an 8 ns access time, meaning the read/write cycle completes within one clock period — no wait states for the controller at that speed. The 9-bit width (8 data + 1 parity or control bit) suits applications where a ninth bit carries a flag alongside the data word, common in telecom or datacom framer interfaces. Depth expansion is supported via cascading multiple devices, and width expansion is also on the datasheet.
Package and reflow — 32-PLCC J-lead on a 5 V rail
Housed in a 32-lead PLCC (J-lead) package, 11.43 x 13.97 mm body, the part is surface-mount but the J-lead geometry demands a specific solder-paste stencil aperture to avoid tombstoning during reflow. The J-lead heel fillet is critical for joint reliability; a 0.15 mm stencil thickness with a 1:1 aperture-to-lead-footprint ratio is typical. Maximum supply current is 40 mA, so the thermal dissipation in the PLCC at 70°C ambient is manageable without forced airflow, but the junction temperature should be checked against the package's RθJA for the specific board layout.
Infineon (formerly Cypress) has marked the CY7C4291-10JXC as Obsolete. The part is not recommended for new designs; existing BOM lines should plan for a replacement or secure a last-time-buy inventory. Confirm the date code and condition (new original, not refurbished) at quote time.