AN2783 datasheet(6/47 Pages) STMICROELECTRONICS

6 / 47 page

Main features

AN2783

6/47

Main features

The PM8800 demonstration kit has been designed to cover several PoE configurations with

easy customization.

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Basic configuration: (high-power applications)

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5 V output

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Up to 4 A output

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250 kHz operating switching frequency

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Flyback topology DCM/CCM

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Board size 70 x 90 mm

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Power Good indication

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Overall efficiency of 85% at full-load condition (Figure 12)

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Prevalence of the auxiliary source with respect to the PoE line (Section 8.7)

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1500 Vrms isolation ensured by the power transformer

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Support for (see BOM options in Section 5):

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5 V and 3.3V output

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diode or synchronous rectification

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standard IEEE802.3af or high-power applications

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non-isolated flyback topology

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Support for class 0-3 (IEEE802.3af) and class 4 (pre-standard modes)

The following 2 basic board configurations are addressed with the same PCB and referred

in the rest of the text as:

–

Standard power: this configuration covers IEEE802.3af applications and it is

based on flyback topology with diode rectification.

–

High power: this configuration targets applications with output power in excess of

the IEEE802.3af standard up to 20 W as output. This configuration is based on

flyback topology with synchronous rectification. The same configuration can be

used in PoE designs targeting high efficiency and/or with wide range auxiliary

input (down to 12 V with prevalence of the auxiliary with respect to PoE).

AN2783 Datasheet(PDF) 6 Page - STMicroelectronics

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