ABSTRACT

　　The intent of this application note is to identify proper component selection for EMI filtering for the Class-D output stages of the AIC31xx and DAC31xx product families. Throughout this application note， the AIC31xx and DAC31xx families will be referring to the AIC3110， AIC3111， AIC3100， AIC3120， DAC3100 and DAC3120， respectively. The AIC31xx and DAC31xx family of highly integrated， high-performance codecs and DAC’s from Texas Instruments include class-D output stages， able to operate in filter-free mode. Normally an L-C filter would be required to eliminate noise and block high frequency content. While the L-C filter may be rendered unnecessary however， many customers still employ EMI filtering at the outputs to pass FCC testing and block very high frequency emissions， typically using ferrite bead inductors and a capacitor. Component selection can become critical for these filters， as the AIC31xx and DAC31xx families employ integrated over-current protection （OCP） circuits， which can be unintentionally tripped due to improper implementation of the EMI filter.