VSC8221 datasheet(49/138 Pages) MICROSEMI

49 / 138 page

VSC8221

Data Sheet

VMDS-10106 Revision 4.1

December 2006

49 of 50

16 ETHERNET IN-LINE POWERED DEVICE SUPPORT

16.1 Cisco in-Line Powered Device Detection Mode

Used to detect in-line powered devices and devices that derive power from CAT-5 cable for their operation in Ethernet network

applications, the VSC8221 device's in-line powered device detection mode can be part of a system that allows iP-phones and

other devices to receive power from an Ethernet cable, similar to office digital phones receiving power from a PBX (Private

Branch Exchange) office switch via the phone cable. This can eliminate the need for an iP-Phone to have an external power

supply, since the Ethernet cable provides power. it also enables the in-line powered device to remain active during a power

outage (assuming the Ethernet switch is connected to an uninterrupted power supply, battery, back-up power generator, etc.).

This mode is disabled by default and must be enabled in order to perform in-line powered device detection. Please refer to http:/

/www.cisco.com/en/US/products/hw/phones/ps379/products_tech_note09186a00801189b5.shtml for additional information.

16.2 in-Line Power Ethernet Switch Diagram

Figure 17. in-line Powered Ethernet Switch Diagram

SMI

Control

Processor

Gigabit Switch/MAC

VSC8221

10/100/

1000BT PHY

MAC

Interface

X-former

RJ-45

I/F

IN-LINE

POWER

SUPPLY

UNIT

CAT-5

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