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

3 Input Stage with Star Ground

To fix this issue, G2, G3, and G4 input stage ground nodes were connected with separate traces directly to the TPA32xx amplifier analog ground reference, G1. With this star ground connection scheme, G1 G2 G3 and G4 are well coupled and share the same ground potential. Therefore, no noise voltage can be developed between the input stage grounds and the TPA32xx analog ground. Figure 6 shows this connection scheme.

figure6_slaa719.gifFigure 6. SE to Diff Input Stage Star Ground

NOTE

The supply grounds of the two operational-amplifiers are not shown to connect to specific point on the grounding scheme. The high PSRR offered by the op-amp means that ground noise on the supply pins will have little impact on the audio performance. Generally it is acceptable to tie the operational-amplifier supply ground to a convenient location.