Synchronous FIFO for rate-matching and short buffers
The Cypress CY7C4205V-15ASXC is a synchronous FIFO memory from the CY7C series, organized as 256 words by 18 bits for a total of 4.5 Kbit of storage. It operates at a 66.7 MHz data rate with an 11 ns access time, making it suitable for rate-matching between asynchronous clock domains or buffering short data bursts in telecom, networking, and imaging pipelines.
66.7 MHz clock and 11 ns access — timing closure for synchronous designs
The 66.7 MHz maximum clock frequency sets the read/write cycle rate; the 11 ns access time from clock edge to data valid defines the output hold and setup margins. In a typical synchronous system, the FIFO's internal pointer logic advances on each rising edge, so the access time directly affects the timing budget for the downstream capture register. The 30 mA maximum supply current is drawn from the 3.3 V rail and scales with clock rate and output loading.
256 x 18 organization — what the 18-bit width buys you
The 18-bit word width accommodates a 16-bit data bus plus two tag or parity bits, common in telecom backplanes and DSP data paths. The 256-word depth is shallow — enough for elastic buffering between clock domains or FIFO-first-in-first-out queuing in a PCI or local bus interface, but not for large packet storage. Depth expansion cascades multiple devices to increase word count while maintaining the same 18-bit width.
Cypress (now part of Infineon) no longer manufactures this FIFO.
Package and temperature grade — board-fit constraints
It is a surface-mount, quad flat pack.