VSC8601 Datasheet
Design Considerations
8.10
High VDD33 and Low VDDIOMAC Supply
Issue: If VDD33 is set to the maximum allowed 3.3 V supply and VDDIOMAC is set to
the minimum allowed 3.3 V supply, the VSC8601 device can experience performance
issues. These issues generally occur in a lab environment and not in typical
applications.
Implications: When VDDIOMAC is set to 3.3 V, VDD33 and VDDIOMAC cannot be
sourced by two different 3.3 V supplies.
Workaround: If using VDDIOMAC in 3.3 V mode, use the same 3.3 V source supply as
the VDD33, using a proper filtering scheme. For more information, see VSC8601 Design
and Layout Guide, which is available on the Vitesse Web site at www.vitesse.com.
Revision 4.1
September 2009
Page 101