VSC8540RT datasheet(24/87 Pages) MICROCHIP

24 / 87 page

VSC8540RT

DS60001603E-page 24

 2022 Microchip Technology Inc. and its subsidiaries

FIGURE 5-9:

EXTERNAL 3.3V REFERENCE CLOCK

Note:

Reference clock source less than

/10 from XTAL1.

Note:

No voltage scaling is required for a 2.5V external reference.

5.6

Ethernet Inline-Powered Devices

The VSC8540RT device can detect legacy inline-powered devices in Ethernet network applications. Inline-powered

detection capability is useful in systems that enable IP phones and other devices (such as wireless access points) to

receive power directly from their Ethernet cable, similar to office digital phones receiving power from a private branch

exchange (PBX) office switch over telephone cabling. This type of setup eliminates the need for an external power sup-

ply and enables the inline-powered device to remain active during a power outage, assuming that the Ethernet switch

is connected to an uninterrupted power supply, battery, back-up power generator, or other uninterruptable power source.

For more information about legacy inline-powered device detection, visit the Cisco website at www.cisco.com. The fol-

lowing illustration shows an example of an inline-powered Ethernet switch application.

XTAL1

270 Ω

± 5%

820 Ω

± 5%

VSC8540RT 数据表(PDF) 24 Page - Microchip Technology