LM5176: Please fine tune compensation design for Vin=12V, Vout=4.75V/12V/20V are compatible

Juin Chen

Part Number: LM5176

Tool/software:

Dear TI experts,

I have one design to change Vout voltage level(4.75V, 12V and 20V three kinds of Vout level) and keep on Vin=12V, but I just want to change RB resistor.

Could you fine tune to optimize compensation design for Rc, Cc1 and Cc2? How can share our schematic for you? I try to upload schematics on E2E but the resolution isn't good. Thanks.

6 months ago

0 Stefan Schauer 6 months ago

TI__Guru 58641 points

Hi Juin,

best for that is to start with the quickstart calculator: LM5176 Design Calculator

Once done you can also attach it here for a review.

Best of course is to check out on the real hardware as then you can also see and consider all the parastic you will have on the PCB.

Best regards,

Stefan

0 Juin Chen 6 months ago in reply to Stefan Schauer

Prodigy 130 points

Hi Stefan,

Is it available that one group compensation design to support Vout=4.75V, 12V and 20V? I don't know how to use design calculator to get optimize compensation design values to support three kind of output voltage level. Thanks.

0 Stefan Schauer 6 months ago in reply to Juin Chen

TI__Guru 58641 points

Hi Juin,

I think this should be possible but with the quickstart calculator this could be better evaluated.

Please give it a try.

Best regards,

Stefan

0 Juin Chen 6 months ago in reply to Stefan Schauer

Prodigy 130 points

Hi Stefan,

Rc is key point to decide loop stability. It is hard to tune better Rc value for 5V and 20V. Do you have good idea? Thanks.

0 Stefan Schauer 6 months ago in reply to Juin Chen

TI__Guru 58641 points

Hi Juin,

please share your Quickstart calculator file with your design parameter entered and I can check.

Best regards,

Stefan

0 Juin Chen 6 months ago in reply to Stefan Schauer

Prodigy 130 points

Hi Stefan,

Please download from the link, Thanks.

drive.google.com/.../view

0 Stefan Schauer 6 months ago in reply to Juin Chen

TI__Guru 58641 points

Hi Juin,

a good starting point would be this settings:

Best regards,

Stefan

0 Juin Chen 6 months ago in reply to Stefan Schauer

Prodigy 130 points

Hi Stefan,

Thanks for your quickly feedback. In loop theory, I would think that crossover freq sets between switch freq/10~switch freq/6. how do you determine cross freq, 10K? please give me your suggestion, Thanks.

+1 Stefan Schauer 6 months ago in reply to Juin Chen

TI__Guru 58641 points

Jiun,

Cross over frequency should be lower then 1/10 of f_SW and less then 1/5 of RHPZ (sometimes 1/3)

So use at least the lower of the two.

So even with the 10kHz I would be still too high better would be to go down to 5kHz - checking in the real hardware would be anyhow the best solution.

Best regards,

Stefan

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LM5176: Please fine tune compensation design for Vin=12V, Vout=4.75V/12V/20V are compatible