Lack of Line Impedance Matching Resistors in FX2 Reference Designs | Cypress Semiconductor
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Lack of Line Impedance Matching Resistors in FX2 Reference Designs
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?
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.