Ripple voltage from output of LM5005

Hi Kim.

Said in this way it is really harsh to understand where could be the problem!
Could you share more information?

Which is your input voltage range?
Output current?

Switching frequency?

Inductance value?
Which component do you select as output capacitor?

Bye

Paolo

Hi Paolo,

     Great to get your reply. Pls see the attached schematic for the power part. PCB is two layers and the inductor(L1) and the capacitors(E1,E2,E3) place underneath of the LM5005(means another layer/surface). Will the noise caused by these?

Thanks

Kim

Hi Kim.

I still don't know which is your output current...

And which is the E3 & E4's ESR?

From your schematic I can understand that you are running your circuit at 300kHz, is it right?

Bye

Paolo

Hi Paolo,

     Output current is around 1A. E3 is aluminium electrolytic capacitor, E4 is tantalum capacitor. Yes, you are right, is 300KHz.

Thanks

Kim

Inductance value seems to be good, ripple current cannot justify the ripple voltage you're observing on your output...

Which is your aluminum capacitor ESR (E3) at 300kHz?

Are you sure that it still working as a capacitor and not as an inductance?

Bye

Paolo

Paolo,

      i do not understand this

Are you sure that it still working as a capacitor and not as an inductance?

Can you explain more.

Thanks

Kim

Hi Kim.

You've to look to the impedance graph...

Each capacitor has a curve in which you can observe a decreasing impedance until the resonance frequency, after that impedance is increasing with frequency, as it would be an inductor...

Can you give me the part number of the capacitor?

Bye

Paolo