DocID031629 Rev 1

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PM8804

Layout guidelines

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6

Layout guidelines

6.1

General guidelines for 48 V converter

The following general guidelines are valid for all the typical converter topologies used for

48 V PoE/PoE+ converters.

The length of the interconnections between the following groups of components belonging

to the primary side of the converter must be kept as short as possible:

1.

Input ceramic capacitors

2.

Input side of the power transformer

3.

Power MOSFET and sense resistors

4.

Active clamp circuitry or snubber circuitry (if present)

The length of the interconnections between the following groups of components belonging

to the secondary side of the isolation must be kept as short as possible

1.

Secondary rectifier diode(s), or synchronous rectifier MOSFET(s) and associated

driving circuitry

2.

Output side of the power transformer

3.

Output ceramic capacitors

Isolation / spacing as required by applicable safety standards must be assured between all

the rails / traces / planes at 48 V and between primary and secondary side of the converter.

Figure 13. PM8804 ground areas (top view)