I am using the TPA3125D2 in exactly the BTL configuration depicted in Fig 30 of the 2008 datasheet. Supplies are perfectly quiet at 24V. I have an additional 20K ohms in series with two audio inputs that are being summed at Rin (return is common at Lin). \SD is tied to 24V; Mute is tied to Gnd. Gain0/1 are both at Gnd for now, but can be switched under firmware control.
I am getting a noise burst at the output every 276 mSec, lasting 52 mSec each. It seems to be white noise, above normal audio frequencies but rail-to-rail and thus audible (deafening, actually) at the output. The board is controlled by a PIC microcontroller with which I have extensive experience, and holding the microcontroller in reset has no impact on the noise, so any interaction with the firmware or other sections of the board seems to be eliminated.
Vclamp is sitting at about 10.6V, and droops by about 200 mV during each noise burst. Not sure if this is a cause, effect, or some other symptom.
Where do I go next?