I built a prototype board for audio output with 2 TAS5760M chips and a PCM1808 for input.
The board is attached to a Papilio One 500k FPGA board.
I designed the board based on "Figure 52. Stereo BTL using Software Control, 32 Pin DAP Package Option" on page 51 of the data sheet, but I added additional 33uH 1uF RC filters on each power supply rail ( PVDD 5V and VDD 3.3V ).
For the output filters I'm using 33uH Lfilt and 1uF Cfilt as per page 3 in sloa119b.pdf
If I pull /SPK_SD low on both chips there is no output as expected.
If I take either chip out of shutdown and output all zero audio data to the other I have audible noise on the output of the chip receiving zeros.
I've tried changing the digital gain, analog gain, volume control, and PWM rate and nothing seems to affect the noise volume or frequency.
I'm trying to figure out what to try next.