Lack of Line Impedance Matching Resistors in FX2 Reference Designs

Question: The FX2 (CY7C68013) reference designs do not show the normal line impedance matching resistors. Also, the manual does not reference them on the host attachment resistor of 1.5 K ohms. What should be the proper values for the FX2?

 

Answer:

This part has all of these components built into the chip. No external parts should be used. The FX2, D+ and D- lines should be connected with as short as possible a trace. They should run parallel to each other and preferably without any trace stubs. This is to maintain the signal quality for the 480/s bit rate these lines carry. Also the characteristics of these lines must be controlled internally due to the requirement of matching both the full and high-speed characteristics.