Intel 815 - Manual (Page 123)

I/O Subsystem
R
Intel
®
815 Chipset Platform Design Guide 123
Figure 63. Recommended USB Schematic
15 k Ω
15 k Ω
15 Ω
15 Ω
47 pF
47 pF
ICH
P+
P-
US
B
co
nn
ecto
r
< 1"
< 1"
90 Ω
45 Ω
45 Ω
Driver
Driver
USB twisted-pair cable Transmission line
Motherboard trace
Motherboard trace
USB_schem
The recommended USB trace characteristics are as follows:
•
Impedance ‘Z0’ = 45.4
Ω
•
Line delay = 160.2 ps
•
Capacitance = 3.5 pF
•
Inductance = 7.3 nH
•
Res at 20
°
C = 53.9 m
Ω
10.5 I/O APIC (I/O Advanced Programmable Interrupt
Controller)
Systems not using the I/O APIC should comply with the following recommendations:
•
On the ICH

Connect PICCLK directly to ground.

Connect PICD0, PICD1 to ground through a 10 k
Ω
resistor.
•
On the processor

PICCLK requires special implementation for universal motherboard designs. See Section
4.2.9

Connect PICD0 to 2.5V through 10 k
Ω
resistors.

Connect PICD1 to 2.5V through 10 k
Ω
resistors.