Xilinx Spartan-6 FPGA Series User Manual

46 www.xilinx.com Spartan-6 FPGA PCB Design and Pin Planning
UG393 (v1.1) April 29, 2010
Chapter 4: PCB Materials and Traces
Simulating Lossy Transmission Lines
Due to the different modeling implementations used by various circuit simulators
(frequency-domain versus time-domain techniques), it is important to check that the
models accurately reflect actual losses. One method is to compare the models against
known published configurations.
Cable
Cables are controlled-impedance transmission lines due to the constant physical
dimensions of conductor and dielectric along the length of the cable. The highest quality
cable shows little variation in these dimensions and also has a wide bandwidth with low
loss at high frequencies.
Connectors
The connectors attached to cables should exhibit low parasitic inductance, low-parasitic
capacitance, and low crosstalk for high bandwidth operation.
Skew Between Conductors
When selecting a cable, look for a specification of the skew between the conductors in a
cable. If the conductors are not length matched, the skew appears in the common mode
and directly reduces the eye height.

Xilinx Spartan-6 FPGA Series Specifications

General

Device Family	Spartan-6
Category	FPGA
Number of Logic Cells	3, 840 to 147, 443
Block RAM	216 Kb to 4, 824 Kb
Maximum User I/O	102 to 576
Process Technology	45nm
Operating Voltage	1.2V
Number of DSP Slices	8 to 180
Package Options	FG256, FG484, FG676, FG900, FG1156, FT256, FTG256, FTG484, FTG676, FTG900, FTG1156