LM5006 input capacitors

what is your input voltage range?

Input voltage range is 6V - 55V.

Vout = 5V

I was thinking if your input was less than 50 V, you could find a 0.1 uF in a 0402 package.  You could most likely squeeze that into your layout.  For other converters I sometimes leave that high frequency bypass capacitor out of the design, but I have not tried it with LM5006.

Hmm.  There's always the chance that I could find room for the current 0603, it's just that I'd rather save the space completely if possible.

I'll often go by the rule of thumb with decaded capacitors in a case like this, but I've also learned that, given the low resistance and inductance of an SMT ceramic capacitor, it doesn't actually buy you much - that basically, if it's close to the pin, an 11uF capacitor is just as good as separate 10uF and 1uF caps.

With that in mind I'm tempted to remove the 0.1uF and ensure that the 1uF is very close to the pin.  I do have a current design that includes the 0.1uF, as well as the LM5006 eval kit.  Any good way to test the effect of leaving off the 0.1uF?  High-frequency noise on the output?  As long as the 1uF is present, you wouldn't expect the regulator to fall out of regulation or anything serious like that, would you?

In general I agree with your assessment.  I can tell you that I have worked with certain parts where the 0.1 uF high frequency bypass is necessary for proper current limit operation ( the internal current detection is sensitive to that HF noise), but that is not necessarily applicable to LM5006.  As I stated previously, I have not used LM5006 personally, so my comments are just general case.  Maybe someone with detailed knowledge of LM5006 can comment.

Sounds reasonable.  Do I go find an LM5006 expert or will one chime in on this thread? 

LM5006 is supported by a different business unit than mine.  I comment a lot on the forum if I have something to contribute, even if it is not a device I directly support.  If no one else responds, I'll see if I can direct you question to the proper support person on Monday.

Hi John,

Any chance of an LM5006 specialist taking a look at this question?

Thanks,

Dave

LM5006 is supported by an entirely different business unit.  I do not know any of them personally.  Let me ask around.

Hi Vijay,

  My C1 is 1uF 0805, and is as close to the pin as possible.  I have about 300uF upstream in aluminum capacitors. 

  If I understand your post correctly, this means that I can remove C5 in my design?

Thanks,

Dave