72Mbit DDR II+ SRAM at 400 MHz — last-time-buy reality
The CY7C2568KV18-400BZC is a 72Mbit synchronous SRAM built on a DDR II+ architecture — it transfers data on both rising and falling clock edges, doubling the throughput per clock cycle compared to a single-data-rate device. The 400 MHz clock rate delivers a peak data rate of 800 MT/s across the 18-bit-wide data bus, a fit for high-bandwidth buffer applications in networking line cards, test equipment, or FPGA-attached data paths that need deterministic read/write latency without DRAM refresh overhead. The memory is organized as 4M x 18 bits — the 18-bit word width maps cleanly to a 16-bit data bus with two parity/ECC bits or to an 18-bit raw-data path. The parallel interface connects directly to a memory controller without serialization latency, which is the reason this class of SRAM persists in designs where QDR or RLDRAM would add controller complexity.
Package and supply — board-fit constraints
The supplier device package is 165-FBGA (13x15) — the 13x15 mm footprint and ball map are the critical dimensions for the PCB layout; the stencil aperture and solder-paste volume for the centre thermal balls must follow the JEDEC design guide for this ball count. Supply voltage is 1.7 V to 1.9 V — a single core rail, but the 200 mV tolerance band means the regulator must hold regulation within ±5 % across load transients. A standard 1.8 V LDO with 1 % initial accuracy and 50 mV dropout at the SRAM's peak current (typically 400–500 mA for a 400 MHz DDR II+ part) keeps the rail inside the window.
Sourcing posture for an obsolete SRAM
Because the CY7C2568KV18-400BZC is officially obsolete, no authorized distributor holds factory stock. The part is sourced through independent channels that maintain surplus inventory from end-of-life buy lots or overstock. Each lot is verified for authenticity and traceability before shipment; the buyer receives a certificate of conformance with the order. A functional replacement would require a board spin — the 165-ball FBGA footprint and the DDR II+ timing parameters are specific to this die revision. The procurement desk should budget for a one-time BOM qualification if the existing design must be migrated to an active SRAM family.