LM5575: AN-1571 Quick Start Guide

hideyuki sakai

Mastermind 6250 points

Part Number: LM5575

Dear, Sir.

My customer has been started the design of LM5575 referring AN-1575

Quick Start Guide.

The document defines as Rfb1(10) & Rfb2(9).

The other side, Formula 9 is defined Rfb1(9).

Which is correct for Formula 9, Rfb1(10) or Rfb2(9)?

Best Regards,

H. Sakai

over 5 years ago

0 Arief Hernadi over 5 years ago

TI__Mastermind 23835 points

Hi,

I will be looking into this

Thanks
-Arief

0 Arief Hernadi over 5 years ago in reply to Arief Hernadi

TI__Mastermind 23835 points

Hi,

Looking into the calculator, you should use the value of Rfb1 or R1 for this formula

Thanks
-Arief

0 hideyuki sakai over 5 years ago in reply to Arief Hernadi

Mastermind 6250 points

Dear, Arief-san.

Thank you so much for your advice.

You mean it is a miss-typing of Rfb1(10).
Is it possible to correct AN-1571 Quick Start Guide?
Because the Guide will be a good reference for beginners.

Best Regards,
H. Sakai

0 Arief Hernadi over 5 years ago in reply to hideyuki sakai

TI__Mastermind 23835 points

Yes that would be correct. Alternatively you can also use the calculator provided at the bottom of this page
www.ti.com/.../toolssoftware

It is under development tools

Thanks
-Arief

0 hideyuki sakai over 5 years ago in reply to Arief Hernadi

Mastermind 6250 points

Dear, Arief-san.

I tried to create the design file using Webench tool. It is as below.

Vout = 12V.

Rcomp = 2.7kOHM based on Rfb1, 976OHM.

Rcomp = 24.2kOHM based on Rfb2, 8.87kOHM.

Which is correct for Fomula (9)? I would like to double-confirm.

Best Regards,

H. Sakai

0 Ambreesh Tripathi over 5 years ago in reply to hideyuki sakai

TI__Expert 6860 points

Sakai-San ,

The Rcomp value will be dependant on Rtop feedback resistor on the potential divider on the VOut . In the Schematic above that is Rfb2 .

Further Rcomp value determine the crossover frequency . In the case of User's guide , it seems the crosover frequency is aimed at 20KHz . In the case of Webench , it will be diffierent and hence you may see a difference in the value of Rcomp and then Ccomp .

You can simply follow the Webench design and verify it on bench .

---Ambreesh

Power management

Power management forum

LM5575: AN-1571 Quick Start Guide