MP7770 –2 X 45W STEREO SE OR 90W MONO BTL CLASS D AUDIO AMPLIFIER

MP7770 Rev.1.0

www.MonolithicPower.com

19

12/4/2012

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prevent crosstalk. Make sure that all inductors

used on a single circuit board have the same

orientation.

Route each power supply from the source to

each channel individually, not serially. This

prevents channel-to-channel coupling through

the power supply input.

Electro-Magnetic Interference (EMI)

Considerations

Due to the switching nature of Class D

amplifiers, care must be taken to minimize the

effects of electromagnetic interference from the

amplifier. However, proper component selection

and careful attention to circuit layout can

minimize the effects of the EMI due to the

amplifier switching.

The power inductors are a potential source of

radiated

emissions.

For

the

best

EMI

performance, use toroidal inductors, since the

magnetic field is well-contained inside the core.

However toroidal inductors can be expensive to

wind. For a more economical solution, use

shielded-gapped–ferrite

or

shielded-ferrite-

bobbin-core inductors. These inductors typically

do not contain the EM field as well toroidal

inductors, but can achieve a better balance

between good EMI performance with low cost.

The size of high-current loops that carry rapidly

changing currents must be minimized: Make

close to the MP7770 as possible.

Nodes that carry rapidly changing voltage, such

as SW, need to be made as small as possible.

If sensitive traces run near a trace connected to

SW, place a ground shield between the traces.