Table of Contents
Advertisement
2.7.2 USB2.0 Routing Guidelines
USB 2.0 Insertion Loss Budget
Figure 18 : USB 2.0 Insertion Loss Budget
COM Express USB implementations should conform to insertion loss values less than or equal to those
shown in the table above. The insertion loss values shown account for frequency dependent material
losses only. Cross talk losses are separate from material losses in the USB specification.
"Device Down" implementations, in which the USB target device is implemented on the Carrier Board,
may add the ferrite and USB connector insertion loss values to the Carrier Board budget.
The Carrier Board insertion loss budget then becomes LC + LD, or 2.68 dB.
Table 22 :USB Insertion Loss Budget, 400 MHz
Segment
Loss (dB)
L
A
L
B
L
C
L
D
L
E
Total
Notes
0.67 Up to 6 inches of module trace @ 0.28 dB / GHz / inch
0.05 COM Express connector at 400 MHz measured value
1.68 Up to 14 inches of Carrier Board trace @ 0.28 dB / GHz / inch
1.00 USB connector and ferrite loss
5.80 USB cable and far end connector loss, per source specification
9.20
７０
Advertisement
Table of Contents
