LNK Series Current Stability

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Hi,

I designed many types of driver with LNK series. Working well. But output current  deviating 50ma up or down continuously (eg. nominal output 800mA). Also when put it in a plastic case and potted output rising +100mA. 

Which precoutions I have to take avoiding from this unstable regulation.

 

Best regards,

 

 

Hi,

 

Can you specify which particular LNK device you are referring to?

Hi,

 

LNK417,LNK418 and LNK419

 

thanks, 

Thanks for the information.

For the 50mA variation, are you referring to ripple current? If the oscillation frequency of the output current is 2x line frequency then it's just the ripple current, which is normal. But you could be referring to the average output current. In this case, I can only think of some noise being injected into the device, which could potentially explain why  potting changes the output current by 100mA.

 

 Vpin and FBpin traces are critical and must be routed properly and away from high-voltage switching node such as drain pin. If noise is induced on these traces, then it is possible to affect the output regulation.

 

 You can try to re-check the layout and see if you can further improve it. Maybe, you can put a small capacitor (100nF) on Vpin or FB pin to determine if it's related to noise.

 

Please also check the potting material characteristics and make sure it has excellent electrical non-conductivity.