Obsolete synchronous FIFO — what you need to know for the BOM
The CY7C4245V-25ASXC is a Cypress synchronous FIFO organized 4K words by 18 bits, clocked at 40 MHz with a 15 ns access time. The part is now listed as obsolete, so any new design-in should be avoided; this is strictly a repair, replacement, or last-time-buy scenario for existing boards. The 4K x 18 depth and width, plus programmable flags and retransmit capability, made this a workhorse for buffering between asynchronous clock domains in telecom line cards, test equipment, and video processing systems.
The 40 MHz data rate and 15 ns access time mean back-to-back reads or writes at full clock speed with no dead cycles, as long as the FIFO is not empty or full. The synchronous interface simplifies the control logic compared to asynchronous FIFOs — just a read/write clock and enable pins. Depth and width expansion are supported if you need larger buffers. Maximum supply current is 30 mA, so the power budget is modest.