LNK623DG Noise Floor Issue

Posted by: Rob Pentley on 02/27/2012

Hi,
We are currently designing a new product that uses the LNK623DG as the PSU controller. Our application must have a noise floor of below -135dB from 0-10MHz. After adding output snubbers and adjusting the input snubber I have achieved a noise floor of -130dB. Please can I have some technical assistance in reducing this further?
Many Thanks,
Rob Pentley

Comments

I am assuming this is an isolated design. Have you tried common mode inductor and Y-capacitors?

Hi
I have attached the schematic for the design
Thanks,
Rob

I have found that the noise floor is reduced further by adding a snubber between Drain and Ground. Are there any adverse effect of doing this? The snubber consists of a 300pF cap in series with a 2K2 resistor.

Try and use a smaller capacitor --maybe 100pF. 300pF is blowing some significant power. Resistor must be hot...