Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel
®
Pentium
®
4 Processor-M and Intel
®
845MP/845MZ Chipset Platform
164 Design Guide
R
Figure 92. Example 3.3-V/V5REF Sequencing Circuitry
VCC Supply
(3 .3 V )
5V Supply
To SystemVREF
To System
1K
1 uF
In compliance with USB 2.0 specification requirements for continuous short conditions, V5REF_Sus
pins must be connected to 5 V. 5VREF_Sus affects 5-V tolerance for all USB signals, both over-current
and data pins. USB 2.0 specification requires that USB controller to withstand a continuous short
between the USB 5-V connector supply to a USB signal at the connector for 24 hours. Figure 93 and
Figure 94 provide options for connecting V5REF_Sus to 5 volts on mobile platforms. Figure 93 is for
platforms that support +V5_Always (5 V always ON). Figure 94 represents a connection to V5REF_Sus
for platforms that do not support +V5_Always.
Figure 93. V5REF_Sus Option 1: +V5_Always Available in Platform
+V5_Always
USB D+
V5Ref_Sus1
V5Ref_Sus2
USB D-
ICH3-M
USB Power (5V)
GND
Customer specific or
Intel recommended
USB interface
circuits
Customer specific or
Intel recommended
USB power circuit
0.1uF