Hi Team
Two question need your support,THX
1. OPA feedback in the LM5039evm circuit (U3 as shown below)
Does this OPA have any tricks or special attention in choosing meal parameters?!
2.Does the RF and CF product parameter have any relationship or limitation with the switching frequency?!
Hello,
1). There is no special requirement to the OPAMP. A normal OPAMP (such as LM324, LM2902...) is fine to meet dynamic performances.
2). RF and CF are filter to affect the response time to the over load. You can take the below value as a good example. The values has no direct relationship with the switching frequency.
Hi Sean
Thank you!
Based on 2).
When we used other controllers before...RF(R13) and CF(C21) should belong to the current sense FILTER
The cut-off frequency of the current sense FILTER should be greater than the switchin frequency
So there is no such relationship here?!
. When we discussed OPA feedback (LM5027A Evaluation Board?)
It looks like the structure in the picture below...Want to ask if CSS will have any side effects if it is added to the powder (1~4.7uF)?! Thank you....
Hi Sean
Thank you!
<1> From the perspective of LM5039-evm... If you want to improve the transient Transient Response!
Is there only be compensation around the blue frame of the secondary side U3 (LMB261) to adjust?!
Would it be helpful to adjust parameters the primary side ofLM50395?!
<2>For feedback compensation
Would you recommend laying an extra set of RC compensation on the COMP pin of the LM5039 (like the red box R8 and C8 in the picture below)?!
Hi Sean
Thank you!
1.Does the loop bandwidth fast or slow have any effect on the product?! (Is it PM and GM stability?)
2.Some products are suggested to lay an extra set of RC compensation on the COMP pin, but some do not. Do you know why is the different?
Hi Sean
Thank you!
Should the parameters of the OPA output feedback U3 affect the transient Transient Response and (PM and GM) stability?!
Usually, what is the suggestion for the selection of U3... Thank you!!
