SLAA719 August 2016 TPA3221 , TPA3244 , TPA3245 , TPA3250 , TPA3251 , TPA3255 , TPA3255-Q1
2.1 Testing Ground Plane Configuration
THD+N vs output power of the TPA3244 amplifier was tested using the SE to Diff input stage where the signal grounds were tied to the ground plane of the PCB as shown in Figure 2. The TPA3244 was setup to run stereo channels in BTL with 4 Ω loads, so our input stage is copied for the other channel.
In Figure 3, the THD+N audio performance looks quite good at 1 KHz. However, as shown by Figure 4, at 100 Hz the THD+N is quite different between channels.
Figure 3. TPA3244 THD+N vs Power 1 KHz Ground Plane
Figure 4. TPA3244 THD+N vs Power 100 Hz Ground Plane
A PCB with the TPA3245 was also tested at 100 Hz and the results were even worse. Channel 1 has a THD+N of 0.013% whereas Channel 2 is 0.0049% at 20 Watts of output power.
Figure 5. TPA3245 THD+N vs Power 100 Hz Ground Plane