Synchronous FIFO for 3.3 V data-path buffering
The Cypress CY7C4225V-15ASXCT is a synchronous FIFO memory with a 1K x 18 organization (18 Kbit total), clocked at 66.7 MHz and delivering an 11 ns access time. The part supports depth and width expansion, includes programmable flags and retransmit capability, and comes in a 64-LQFP surface-mount package. This is a commercial-temperature (0°C to 70°C) device intended for controlled indoor environments such as telecom line cards, data-acquisition front ends, and test equipment where a moderate-depth synchronous buffer is needed.
66.7 MHz clock and 11 ns access time — timing margin in practice
The 66.7 MHz maximum clock rate sets the data-throughput ceiling at 66.7 million 18-bit words per second. The 11 ns access time from the read clock edge to data-valid on the bus is the number to budget in your timing closure. At 66.7 MHz the clock period is 15 ns, leaving 4 ns of margin between the access time and the next clock edge — enough for moderate board trace delays, but not for heavily loaded busses or long PCB runs. If your system runs at a lower clock rate, the margin improves proportionally. The synchronous architecture means the FIFO latches data on every clock edge, so the read and write pointers advance without external handshake logic — the trade-off is that you must provide a clean, free-running clock within the supply and temperature range.
1K x 18 memory — what the organization means for your data word
The 18-bit word width (1K x 18) is a deliberate choice: it maps directly to a 16-bit data bus plus two extra bits for parity, control tags, or sideband signalling. If your application uses a narrower bus, the extra bits can be left unused or tied off, but the FIFO depth is fixed at 1,024 words. For a 16-bit data path with byte-wide parity, this is a natural fit. The part does not support First-Word Fall-Through (FWFT) — the first word appears on the outputs only after the first read clock edge following a write, not immediately. If your design relies on FWFT for zero-latency reads, this part requires a different architecture.
Obsolete — sourcing strategy for sustainment
The CY7C4225V-15ASXCT is officially classified as Obsolete.
Package and temperature — rework and deployment notes
Do not use this part in industrial enclosures, outdoor telecom cabinets, or automotive applications without active temperature management. The 30 mA maximum supply current is modest, but the 64-pin package has no exposed thermal pad — ensure adequate airflow or forced convection if the ambient temperature approaches the upper limit.