Hey there,
We have a design that uses two TAS3204 chips, and it's having trouble passing C.E. in the emitted RFI test, specifically with an RCA attached, at 135mhz we're between 5 and 10 dB over the acceptable limit.
The board is designed well, we have ferrites isolating all power supply lines, also between analog and digital grounds. There aren't any ground loops.
Shielded case has little effect, the closest we can come is by putting a ferrite choke over the power supply cable, and also the RCA cables. It gets the noise down to 4db over the limit. We tried ferrite pads on top of the chip and under the board where the chip is, it had almost no effect.
The unit has potentially 10 rca cables connected at a time, so putting ferrite chokes on all of these cables is not feasible in a consumer level product.
Any thoughts / tips / things we should look for? The circuit design itself was based around the EVM schematics, though I don't know if the EVM would pass CE either.
Any tips or recommendations, or "gotcha" mistakes to look out for would be most appreciated.
~David