TPS54620 parallel operation

Lin Sha

Other Parts Discussed in Thread: TPS54620

Hi,

I have connected two TPS54620 buck converters in parallel operation, I have followed the schematic diagram of the parallel operation in the product folder. However, when I increase the output load current, one of the buck converter output current will increase and the other one will decrease and become negative, can anyone help to see why like this? By the way, the output voltage is very stable which is 5V.

Thank you.

over 9 years ago

0 JohnTucker over 9 years ago

TI__Guru**** 191445 points

TPS54620 is not really designed to operate in parallel. The circuit detailed in this application report
www.ti.com/.../slva389.pdf
is really more of an academic exercise. It is possible to operate them in parallel, but no intrinsic way to make them share current equally. By tying the COMP pins together, you get some measure of current sharing as the peak switch current is proportional to COMP pin voltage, but the exact proportion will be different for each IC. Also, that circuit is very much dependent on PCB layout for proper operation. The COMP pin is very noise sensitive.

0 Lin Sha over 9 years ago in reply to JohnTucker

Prodigy 40 points

Hi John,

Thank you for the reply, as I have read the application report, it shows that connect two in parallel and the current share is around 48% and 52% separately, I use the TPS54620 EMV module to achieve the parallel operation, so is that possible to achieve that nearly equal current share? Anything else need to take note?

Thank you.

0 JohnTucker over 9 years ago in reply to Lin Sha

TI__Guru**** 191445 points

If you are using 2 EVMs wired together, you probably are not couple tightly enough for close current sharing. We used a dedicated PCB with 2 TPS54620 circuits to develop that application. We found that layout was critical for proper operation.

0 Lin Sha over 9 years ago in reply to JohnTucker

Prodigy 40 points

Hi John,

Do you mean the two Vout pin or the COMP pins not couple tightly enough?

Thank you.

0 JohnTucker over 9 years ago in reply to Lin Sha

TI__Guru**** 191445 points

While it is important to keep the output impedance matched, we found that COMP is the critical signal.

0 Lin Sha over 9 years ago in reply to JohnTucker

Prodigy 40 points

Hi John,

Ok, I will try to modify my circuit, thank you very much.

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TPS54620 parallel operation