We have a board with TPA3111D1 that has some noise we would like to quash. The current artwork has the 3111 power and analog grounds tied together, as on the eval board. Since the noise is generated when the 3111 is enabled and (of course) there is not a lot of room for additional decoupling and such (tight board), we are looking at modifying the current path for PVCC and PGND to steer the large switching currents away from the lower level analog signals. Ideally we would like to separate the AVCC/AGND and PVCC/PGND back through separate paths to the power supply (star arrangement). Since the AVCC/AGND currents should be fairly small - they are essentially just for input signal reference, right? - it makes sense to me to run them sort of as signal traces from the AGND plane, and tie the PGND and GND pins (3&4) to the central thermal pad and the power ground plane. The intent is to keep the AGND as clean a possible for the other low current amplifiers and microphone preamp on the board.
With the inductance of the traces and perhaps some ferrite in the mix, there is potential (haha) that the AGND and the other grounds would be at slightly different voltages - I'm guessing a few 10s of mV worst case. My question is how are these grounds wired internally in the chip and could they handle that sort of voltage offset? Will my notion on this work or am I missing something? Any other suggestions appreciated.
