audible noise in LNK306

1.-Varnish the transformer.
2.-Design a transformer with lower flux density.

We are not using any transformer...our design is non isolated type -only two 1mH coils are in our circuit...

Was this issue ever resolved in any way? I have tried several things to reduce the noise when the circuit is loaded, but I have not been able to fix it. Please help if you can.

Have you tried different inductor types? Try inductor rated for higher current to bring down flux density

I also have similar problems with my design. I changed capacitors and inductors, but there is stil a noise. Does inductor with higher rated current solved the problem, or there is something else that I should take care (wire wound, not wirewound, or something else)?

First you have to find the noisy component,

If it transformer; 

you can check the leakage inductance of the transformer, and try to decrease it,

Or you can try to glue or varnish the transformer to see if it is mechanical problem or not, 

If it is Clamp cap. You can try Zener+TVS clamp,

In attachment is my schematic. I followed AN-37.

Noise is made by L2 and C24 which is ceramic capacitor. I figured it out, because when I connected them to PCB using wires, noise is lower.

I change C24 to tantalum, and it's OK. I tried to glue L2, but it's the same. It still make noise. After that, I replace it with 680uH/2,5A (overkill, but that was what I had) and there wasn't noise anymore, but when I turn on relay (consumption increase for 40mA) LNK restarts. After that I bought RFB0807-681L, and change L2 with it, there is still a noise, but lower. So, is there any upper limit for L2 saturation current?

Regards.