MIC2550A(2004) View Datasheet(PDF) - Micrel

Part Name

Description

Manufacturer

MIC2550A
(Rev.:2004)

Universal Serial Bus Transceiver

Micrel 

MIC2550A

PCB Layout Recommendations

Although the USB standard and applications are not based in

an impedance controlled environment, a properly designed

PCB layout is recommended for optimal transceiver perfor-

mance. The suggested PCB layout hints are as follows:

• Match signal line traces (VP/VM, D+, D–) to

40ps, approximately 1/3 inch if possible. FR-4

PCB material propagation is about 150ps/inch,

so to minimize skew try to keep VP/VM, D+/D–

traces as short as possible.

• For every signal line trace width (w), separate

the signal lines by 1.5–2 widths. Place all other

traces at >2w from all signal line traces.

• Maintain the same number of vias on each

differential trace, keeping traces approximately

at same separation distance along the line.

• Control signal line impedances to ±10%.

• Keep RS as close to the IC as possible, with

equal distance between RS and the IC for both

D+ and D–.

Micrel

May 2004

9

M9999-051004

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