MP7748 – 2X20W STEREO SINGLE ENDED CLASS D AUDIO AMPLIFIER

MP7748 Rev. 1.0

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16

1/28/2011

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coupling through the power supply input.

Electro-Magnetic

Interference

(EMI)

Considerations

Due to the switching nature of the Class D

amplifier, care must be taken to minimize the

effects of electromagnetic interference from the

amplifier. However, with proper component

selection and careful attention to circuit layout,

the effects of the EMI due to the amplifier

switching can be minimized.

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 field as well toroidal inductors, but

usually can achieve a better balance of good EMI

performance with low cost.

The size of high-current loops that carry rapidly

changing currents needs to be minimized. To do

are as close to the MP7748 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.