TPS650864: Unused Buck converter

na na78

Guru 16770 points

Part Number: TPS650864

Let me confirm the connection of unused BUCK converter for TPS650864.

There are following pins for BUCK3.

- PVIN3

- LX3

- FB3

I think that FB3 should be connected properly to work the sequence.

So should we need external L, Cout and Capacitor @PVIN3 even if the BUCK3 is in unused?

BestRegards

over 5 years ago

0 Kevin LaRosa over 5 years ago

TI__Genius 17380 points

Hello,

PVIN3 will need to be connected to the V5ANA supply.

Assuming you are using TPS6508640 (TPS650864 has 4 separate unique orderables by the way, so please clarify in any future posts which orderable), you will need to ensure that FB3 receives the expected voltage. If your system can provide this, then there is no need to install L / Cout / Cin.

0 na na78 over 5 years ago in reply to Kevin LaRosa

Guru 16770 points

Hi Kevin

Thank you for your reply.

I assume to use TPS6508640.

>PVIN3 will need to be connected to the V5ANA supply.
All PVINx will need to be connected to the V5ANA supply. Is it correct?

Is BUCK3_PG register enabled internally by providing 1.2V to FB3 from external regulator?

BestReagards

0 Kevin LaRosa over 5 years ago in reply to na na78

TI__Genius 17380 points

Correct.

0 na na78 over 5 years ago in reply to Kevin LaRosa

Guru 16770 points

Sorry, one more question.

> If your system can provide this, then there is no need to install L / Cout / Cin.

Do you mean it is not necessary to connect PVINx to V5ANA supply too?

BestRegards

0 Kevin LaRosa over 5 years ago in reply to na na78

TI__Genius 17380 points

Hello,

That is not what I mean. As I explicitly stated in my previous post, you must still connect PVIN3 to V5ANA.

What I mean is that the input capacitor that is normally required next to PVIN3 is not required if there is no power being drawn from PVIN3.

0 na na78 over 5 years ago in reply to Kevin LaRosa

Guru 16770 points

Sorry for my poor understanding.

If BUCK3 is not used in TPS6508640 but want to proceed power sequence, following configuration are allowed?

PVIN3 : V5ANA without Cin
LX3 : Open
FB3 : 1.2V from ext VR

BestRegards

0 Kevin LaRosa over 5 years ago in reply to na na78

TI__Genius 17380 points

Yes

0 na na78 over 5 years ago in reply to Kevin LaRosa

Guru 16770 points

Thanks!

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TPS650864: Unused Buck converter