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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—General Hardware
Design Considerations
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
HDD February 2007
40 Document Number: 305261; Revision: 004
To maintain signal integrity and minimize end-users termination mismatch, the
IXP45X/IXP46X network processors require external series termination resistors. The
value of terminating resistors is based on the operational speed and length of the
transmission line. It is recommended to start with a 18-Ω resistor and adjust the value
if required.
Note: In Figure 11, the series termination for the Host port is 20 Ω, however, Figure 12
recommends using 18 Ω for the Device port.
3.8.2 Device Connection
Figure 11. USB Host Down Stream Interface Example
15 KΩ
20 Ω
22 pF 22 pF
FERRITE
FERRITE
47 µF
0.1 µF
4.7 µF
0.1 µF
22 pF
FERRITE
22 pF
200 mA
USB
Port
20 Ω
USB_VDD
Intel
®
IXP46X
Product Line
Network Processor
USB_HPOS
(D+)
USB_HNEG
(D-)
USB_HPEN
USB_HPWR
Device
1.5 KΩ
USB_3V3V_BUS
Host Device
D
+
D-
15 KΩ
Look at
Note 1&2
B4105-002