Micrel, Inc.
MIC2555
PCB Layout Recommendation
Although the USB standard and applications are not
based in an impedance-controlled environment,
a
properly designed PCB layout is recommended for
optimal transceiver performance. The suggested PCB
layout hints are as follows:
•
Match signal line traces (VP/VM, D+ D–) and try to
keep them 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.
•
•
Control signal line impedances to ±10%.
Keep Rseries as close to the IC as possible, with
equal distance between Rseries and the IC for both D+
and D–.
M9999-060805
(408) 955-1690
June 2005
28
MICREL [ MICREL SEMICONDUCTOR ]
