TPS548A28: SS/REFIN

Sandra Pradeep

Part Number: TPS548A28

Hi TI Team,

We plan to use the TPS548A28RWWR regulator in our new design and did a simulation for the same using TI webench.

In the simulation a 120nF cap is connected from SS/REFIN pin to AGND, but in the datasheet is not recommended to connect a cap between SS/REFIN and the AGND pin.

Kindly let us know which to follow...

Thanks & Regards

Sandra

over 1 year ago

0 David_Daniels over 1 year ago

TI__Mastermind 24105 points

Connect a ground of SS capacitor to VSNS– pin.

If two capacitors are used on SS pin connect larger value SS cap to VSNS-.

Connect smaller value SS cap to AGND. Keep the SS to AGND less than 22nF

0 Sandra Pradeep over 1 year ago in reply to David_Daniels

Intellectual 300 points

Hi David,

Thanks for your reply!

We are not using two capacitors.

As per the simulation schematics from TI webench, we connected a 120nF cap from the SS pin to AGND.

But in the datasheet, it is not preferred to connect a cap between the SS pin and AGND.

So, for the single capacitor use case can you confirm which method to follow?

0 Calan Elaya over 1 year ago in reply to Sandra Pradeep

TI__Genius 11465 points

Hello,

David is out for today. A response will be posted by tomorrow.

Thank you,

Calan

0 Tahar Allag over 1 year ago in reply to Calan Elaya

TI__Mastermind 32400 points

Hello Sandra,

Connect a ground of SS capacitor to VSNS– pin as recommended in the datasheet.

Thanks!

Tahar

0 Sandra Pradeep over 1 year ago in reply to Tahar Allag

Intellectual 300 points

Hi,

From the webench simulation, we have a cap between SS pin and AGND. Did you mean we need to Depop this cap and connect between SS pin and VSNS- ?

I Assume this cap in the simulation is for the soft start delay in the simulation. So if this is removed, how do we handle the overshoot during the charge of the soft start capacitor?

Do let us know how to proceed