SLOA339 July   2024 TAS2764 , TAS2764 , TAS2780 , TAS2780 , TAS2781 , TAS2781

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Capacitor Only Connected at the Class-D Outputs
    2. 1.2 LC Filter Connected at the Class-D Outputs
    3. 1.3 Ferrite Bead Filters
  5. 2EMI Filter Considerations
    1. 2.1 Impedance Consideration of EMI Filter
    2. 2.2 Device Reliability Constraint for High Output Voltage
    3. 2.3 EMI Filter Current Reliability
  6. 3Post Filter Feedback
  7. 4Loop Stability With Post Filter Feedback
  8. 5User Guide: EMI Filter Modeling and Post Filter Feedback Validation Tool
  9. 6Summary
  10. 7References

Abstract

Class-D amplifier outputs are switching outputs, having carrier frequency along with the audio signal content. These switching frequencies lead to concerns with EMI radiation due to long traces running to speaker loads. To meet the EMI radiation specs like FCC/CE, Class-D amplifier outputs typically have EMI filters. In this application note we briefly describe the different techniques used to select and realize EMI filters . The Post filter Feedback feature in TAS27XX family of devices is also explained and filter selection care abouts regarding the same are also listed. The audio amplifier performance is also measured in the presence of the bead. Further an excel sheet based calculator is provided to the user to help assess the feasibility of EMI filter to be used for post filter feedback with some examples.