The CY7C4251-15AC is marked Obsolete by Infineon Technologies.
10 ns access time and synchronous operation
This is a synchronous FIFO with a 10 ns access time and a 66.7 MHz data rate — the access time sets the minimum read-cycle window, so the controller must meet that setup/hold timing to avoid data corruption on the bus. The 72K memory is organized as 8K x 9 bits, with the ninth bit often used for parity or data tagging in FIFO applications like rate-buffering between asynchronous clock domains.
32-TQFP package and board integration
Housed in a 32-TQFP (7x7 mm) surface-mount package — the 0.8 mm pitch requires standard SMT assembly; no special via-in-pad or microvia fan-out is needed for a two-layer board. Supports depth and width expansion via the Expansion Type pins, and programmable flags are available for almost-full/almost-empty thresholds — useful for flow control in multi-FIFO designs.