5Refsus Design Guidelines; Figure 119. Example V; Figure 120. V5Refsus With +V5Always Connection Option; Sequencing Circuitry - Intel 852GM Design Manual

R

Figure 119. Example V

12.4.3.3. V
5REFSUS
The same rule for V
derived from the V
a result, V
V _
CCSUS3 3
In order to meet reliability and testing requirements for the USB interface, the following design
recommendations for the V
USB specification regarding continuous short conditions must be addressed. The USB 1.1 specification
requires host controllers to withstand a continuous short between the USB 5-V connector supply and a
USB signal at the connector. However, the duration is unspecified. The USB 2.0 specification requires
this duration to be at least 24 hours. This in turn requires that the V
attached USB devices are powered. The recommendation is to provide a +V5ALWAYS (active S0-S5)
supply to the V
from S3 and support for self-powered USB devices are not required, then option shown in Figure 121
can be used. V
(active S0-S5).

Figure 120. V5REFSUS With +V5ALWAYS Connection Option

®
Intel 852GM Chipset Platform Design Guide
/ V

Sequencing Circuitry

5REF 5REFSUS
Design Guidelines
also applies for V
5REF
and therefore, the V
CCSUS5
_ will always be powered up before V
5REF SUS
rail from the V rail, this rule must be comprehended in the platform design.
CCSUS5
pins of the ICH4-M should be followed. There are changes to the
5REF_SUS
pin if available as shown in Figure 120. However, if support for wake on USB
5REFSUS
can be supplied by combination of +V5S (active in S0 only) and +V3ALWAYS
5REFSUS
+V5ALWAYS
V5REF_SUS1
V5REF_SUS1 V5REF_SUS2
ICH4 - M ICH4-M
USB D+ USB D+
USB D- USB D-
Intel 852GM Platform Power Delivery Guidelines
_ . However, in most platforms, the V
5REF SUS
_ rail will always come up after the V
CCSUS3 3
_ . In platforms that do not derive the
CCSUS3 3
5REFSUS
0.1 µF
Customer specific or Customer specific or
Intel recommended Intel recommended
USB interface USB interface
circuits circuits
_ rail is
CCSUS3 3
rail. As
CCSUS5
pin be at 5 V as long as the
Customer specific or Customer specific or
Intel recommended Intel recommended
USB power circuit USB power circuit
USB Power (5 V)
GND GND
219