LM5026：LM5026(U3A)/5041(U4B) Feedback loop Compensation

Hi John

Can you tell me the datasheet name? I don't find the U3A and U4B in the datasheet of LM5026 and LM5041.

BR

Jerry Xu

Hi Jerry,

Thanks for your reply.

Please see attached link.(LM5026-page26，LM5041-page14).

https://www.ti.com/lit/ds/symlink/lm5026.pdf?ts=1640063123104&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DLM5026%2526nr%253D105

https://www.ti.com/lit/ds/symlink/lm5041.pdf?ts=1640063141606&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DLM5041%2526nr%253D94

Best Regards,

I know “The schematic in page 14 of the LM5041 datasheet shows such a scheme.

U4A is the error amplifier. C35, R35, C36, R42, C40 and R32 make up the type III compensation network.”

reference attached link.

So,what is the role of U4B.

 https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/888827/lm5041-feedback-loop-compensation/3343100?tisearch=e2e-sitesearch&keymatch=LM5041#3343100

Hi Jerry,

Thanks for your reply.

Does the application circuit use Type2 + Type3 for feedback control circuit.

For example:LM5041 application circuit,Type2=U4B(LM6132) + Type3=U4A(LM6132),reference attached link,pls.

www.ti.com/.../snva074a.pdf

and then , I think I found the answer to the question...the feedback control circuit need C42 (reference attached link,page14.)?

I found LM5026 & LM5041's Datasheet does't describe the capacitor that provide U3(photocouple) bias volt.

Now,I try to uesd the circuit.Finally,It is can work.but load & line regulation over 5-10%.I will tune it again.

if you have any suggestion,tell me pls.

Hi John

So you think cap42 is the reason why the compensator loop use U4B?

BR

Jerry Xu

Hi Jerry,

like you said before. I think LM5026(U3A)，LM5041(U4B) is the error amplifier to attenuate the high frequency noise.

I guess Datasheet's typical application circuit lost cap.but I'm not sure...

If you have any good idea let me know by email,pls.

I will click [This resolved my issue].Thanks your help.

Ok, got your point. Sometimes datasheet can make mistakes.

BR

Jerry Xu