SLAA719 August   2016 TPA3221 , TPA3244 , TPA3245 , TPA3250 , TPA3251 , TPA3255 , TPA3255-Q1

 

  1.   TPA32xx Analog Input Grounding for Single Ended Inputs
    1.     Trademarks
    2. 1 Single Ended to Differential Input Stage
    3. 2 Input Stage with Ground Plane
      1. 2.1 Testing Ground Plane Configuration
      2. 2.2 Ground Plane Results
    4. 3 Input Stage with Star Ground
      1. 3.1 Testing Star Ground Configuration
    5. 4 TPA32xx Ground Pin Reference

2.2 Ground Plane Results

The reason for different THD+N results between stereo channels at 100 Hz is simply ground plane noise. At low audio frequencies and high output power, ground noise is being injected into our SE to Diff analog input stage and reducing performance. However since we cannot control the currents in the ground plane and it is unlikely that the layout is 100% symmetric, the SE to Diff input stage of Channel 1 has been affected more by our ground noise.