MP7722 – 2 x 20W CLASS D STEREO SINGLE ENDED AUDIO AMPLIFIER
MP7722 Rev. 1.5 www.MonolithicPower.com 10
1/22/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
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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 as 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 this, make sure that the V
DD
bypass
capacitors and the Schottky Catch diodes are
as close to the MP7722 as possible.
Nodes that carry rapidly changing voltages,
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.
