Boosted class-D amplifiers drive speakers with voltages greater than the supply voltage. These amplifiers are becoming more common because they allow higher performance audio from a single lithiumion battery. Most boosted class-D amplifiers, however, do not give the user access to the internal boosted oltage. This makes it difficult to multiplex a speaker to multiple audio sources using common analog switches. This application note discusses how the Beyond-the-Rails capability of the MAX14689 allows it to switch these signals without additional circuitry.
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