QDR II synchronous SRAM at 250 MHz — what it buys you
The Cypress CY7C1313KV18-250BZXI is a 18Mbit QDR II synchronous SRAM organized as 1M x 18, clocked at 250 MHz. QDR II (Quad Data Rate) eliminates the dead bus-turnaround cycles that standard synchronous SRAMs incur when switching between read and write — the separate read and write ports let you pipeline back-to-back transactions at full clock rate. That matters in network packet buffers, test equipment capture memories, and any design where the bus cannot stall for a turnaround cycle.
250 MHz — timing margin and bus throughput
At 250 MHz the clock period is 4 ns. With QDR II's double-data-rate on both read and write ports, the effective data rate per pin is 500 Mbps. The 18-bit-wide data bus delivers a raw bandwidth of 9 Gbps. For the layout engineer, the 165-FBGA (13x15 mm) footprint requires controlled-impedance traces and matched-length routing on the clock and strobe lines to hold setup/hold margins. The supply tolerance (1.7V–1.9V) is tight — a 1.8V rail with ±3% regulation is the practical choice; a switching regulator with 50 mV ripple will eat into the timing budget.
For a BOM cost engineer, that means no forced redesign cycle from a supplier-initiated EOL. Because QDR II parts have a narrower second-source base than commodity DDR SRAM, locking in a supply agreement for production volumes is worth the conversation now rather than during an allocation window.