LM5046: LM5046 - COMP Pin Related, Controlling Primary Current Only

Abhinav Soni

Part Number: LM5046

Hey All,

I have a question about the LM5046 (Phase-Shift Controller), I am doing current control for the PSFB application, I checked that the COMP pin takes input as current, Is there any other way to converter voltage equivalent (current sense) feedback to current apart from using an optocoupler or OTA?

Best Regards

Abhinav

over 2 years ago

0 Sean Xu over 2 years ago

TI__Genius 14580 points

Hello,

COMP pin takes voltage feedback from optocoupler. The current is connected to CS pin.

Regards,

Sean

0 Abhinav Soni over 2 years ago in reply to Sean Xu

Prodigy 50 points

Hey Sean
I checked it says the optocoupler sources current into the current mirror connected to the COMP pin, and I need to avoid Opto for a particular application, I have voltage feedback, so do I use an OTA to source current into the COMP pin?

Best Regards
Abhinav

0 Sean Xu over 2 years ago in reply to Abhinav Soni

TI__Genius 14580 points

Hi, Abhinav,

I think so because internal NPN need current source input.

Regards,
Sean

0 Abhinav Soni over 2 years ago in reply to Sean Xu

Prodigy 50 points

Hey Sean

Yes, I thought so, also the datasheet says the voltage rating for COMP pin at -0.3V, is it due to the current sink nature of COMP pin?

Best Regards

Abhinav

0 Sean Xu over 2 years ago in reply to Abhinav Soni

TI__Genius 14580 points

Hi, Abhinav,

This is for ESD protection. When the voltage is less than -0.3V, ESD can conduct. This need be avoided.

Regards,
Sean

0 Abhinav Soni over 2 years ago in reply to Sean Xu

Prodigy 50 points

Hi Sean
I think I get it now, also can I drive current into COMP pin using a voltage-controlled current source like driving the base of an NPN transistor with emitter connected to the COMP pin?

Best Regards

Abhinav

+1 Sean Xu over 2 years ago in reply to Abhinav Soni

TI__Genius 14580 points

Hi, Abhinav,

Yes, I think it is doable.

Regards,
Sean

0 Abhinav Soni over 2 years ago in reply to Sean Xu

Prodigy 50 points

Thanks, Sean!

Best Regards

Abhinav

0 Sean Xu over 2 years ago in reply to Abhinav Soni

TI__Genius 14580 points

You are welcome.

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LM5046: LM5046 - COMP Pin Related, Controlling Primary Current Only