Lower cost, little lost

-- EDN, 1/6/2000

Xilinx's newest FPGA architecture, Spartan-II (Picture), has a confusing name. Although the designation might indicate features similar to those of the company's earlier Spartan and Spartan-XL families, Spartan-II actually is a lower cost version of the company's Virtex FPGAs (see "Programmable-logic heavyweights pack a punch," EDN, Nov 20, 1997, pg 18). As such, it represents a fairly significant upgrade of the first generation Spartan devices, which the company based on the even older XC4000 product families (see "FPGA blue-plate special: extra memory, hold the cost," EDN, Jan 15, 1998, pg 20).

For Spartan-II, Xilinx migrated the 0.22-µm, five-layer-metal Virtex architecture to a mixed 0.18-µm interconnect and 0.22-µm transistor, six-layer-metal process. Xilinx has modified the Virtex power-management scheme, replacing the two temperature-diode pins with a power-down input and power-down-status output. Spartan-I also preserves both device configuration and register status while in power-down mode.

The 2.5V Spartan-II has substantial differences from the 5V Spartan and 3.3V Spartan-XL. Spartan-II includes both look-up-table-based SelectRAM and dedicated BlockRAM, as well as four on-chip digital delay-locked loops, and it supports partial reconfiguration. Spartan-II FPGAs also offer a more extensive set of standard I/O options, including multiple stub-series-terminated-logic (SSTL), high-speed- transceiver logic (HSTL), and Gunning-transceiver-logic (GTL) variants and 5V-tolerant inputs. This greater capability comes at a price, though; in core voltage, footprint, and configuration bit stream, Spartan-II is incompatible with its predecessors, so, to use it, you have to redo your Spartan- or Spartan-XL-based designs.

Table 1 shows the planned Spartan-II devices, their respective logic and memory densities, packaging options, and prices. The XC2S50, XC-2S100 and XC2S150 are currently available for sampling, and Xilinx claims that all five devices will be in production by the end of this quarter. Version 2.1i of Xilinx's Alliance and Foundation software tool sets supports Spartan-II, and intellectual-property support, including the all-important PCI cores, is also in place.

Xilinx Corp, 1-408-559-7778, www.xilinx.com.

—by Brian Dipert