UC1843: UC1843 current sharing — can we tie COMP pins together?

Alexandre Bezier

Prodigy 30 points

Part Number: UC1843

Tool/software:

Hi,

Is it acceptable to tie the two COMP pins directly?

Won’t the two COMP outputs fight (each EA sources current)?

I know the usual advice is to configure the slave EA as a follower but here not possiblev (no access to V+)

6 months ago

0 Adhvaidh Aravind 6 months ago

TI__Expert 4810 points

Hi Alexandre,

I found a similar question on E2E, that was posted a few years ago. Please refer to this link below:

(+) UC1843: COMP pin of one of the controllers to the COMP pin of the other - Power management forum - Power management - TI E2E support forums

Thanks.

Best,

Adhvaidh

0 Alexandre Bezier 5 months ago in reply to Adhvaidh Aravind

Prodigy 30 points

Hi Adhvaidh,

Thanks for your response.

So, I can impose an external voltage on Vcomp directly?Is this safe for the internal EA that sources ~0.8 mA?
Also, how should VFB pin be wired in this case. To the ground ? floating?

Thanks

Alex

0 Adhvaidh Aravind 5 months ago in reply to Alexandre Bezier

TI__Expert 4810 points

Hi Alexandre,

Could you please provide more information about your system.

COMP pin is the error amplifier compensation pin. Connect external compensation components to this pin to modify the error amplifier output.

Alexandre Bezier said:
how should VFB pin be wired in this case. To the ground ?

It depends on your system. Please refer to section 7.3.4 in the datasheet:

Best,

Adhvaidh

0 Alexandre Bezier 5 months ago in reply to Adhvaidh Aravind

Prodigy 30 points

Hi Adhvaidh,

Thanks for your help.

To be more accurate, in my system, the voltage regulation loop is implemented externally using an operational amplifier as an external compensator. (I do not use Optocoupler). Therefore, the internal error amplifier of the UC1843 is not used.

In this configuration, I connect the output of the external error amplifier directly to the COMP pins of several UC1843 devices. This way, all controllers share the same control voltage, allowing current sharing between converters.

Is it possible to do this directly (i.e., drive multiple UC1843 COMP pins from the same external error amplifier output)?

0 Adhvaidh Aravind 5 months ago in reply to Alexandre Bezier

TI__Expert 4810 points

Hi Alexandre,

I am looking into this. I will get back to you as soon as possible.

Thanks.

Best,

Adhvaidh

+1 Adhvaidh Aravind 5 months ago in reply to Adhvaidh Aravind

TI__Expert 4810 points

Hi Alexandre,

Apologies for the delay, and we really appreciate your patience.

Short answer, yes, you can use an external error amplifier to the COMP pins of "n" number of UC1843.

Make sure that the error amplifier specification matches with the specifications highlighted below:

Important to note that the error amplifier should be able to

Sink: n * I_(snk)
Source: n * I_(src)

_Best,

_Adhvaidh

0 Alexandre Bezier 5 months ago in reply to Adhvaidh Aravind

Prodigy 30 points

Hi Adhvaidh,

Thanks for your response. It helps me a lot.

Best

Alex

0 Adhvaidh Aravind 5 months ago in reply to Alexandre Bezier

TI__Expert 4810 points

You're most welcome, Alex.

Best,

Adhvaidh