LM5146-Q1-EVM12V: AGND and PGND connection in EVM PCB

Sahil Gupta

Part Number: LM5146-Q1-EVM12V
Other Parts Discussed in Thread: LM5146-Q1, LM5146, LM5145

Tool/software:

Hi,

I am trying to find how AGND and PGND are connected in LM5146-Q1 EVM.

When I see all the four layer in EVM user guide, I am not able to see where exactly is the connection between AGND(analog ground) and PGND(power ground) are physically connected.

I see R7, R8, C26 (SS, EN/UVLO, RT) components connected together on a plane AGND on top layer, but unable to see how are they connected to PGND.

Can you please help me in knowing this?

thanks a lot,

Sahil

8 months ago

0 Timothy Hegarty 8 months ago

TI__Guru 68757 points

Hi Sahil,

AGND and PGND are tied together as a star-connected ground at the "die attach pad" (DAP) or thermal pad of the IC. It's good practice to have an AGND island for the small-signal components (RT resistor, lower feedback resistor, SS cap) and then connect this to PGND at a single point, typically at the DAP.

Also, use a solid GND plane on layer 2 under the power stage – see the LM5145 and LM5146 EVM layouts for reference.

Regards,

Tim

0 Sahil Gupta 7 months ago in reply to Timothy Hegarty

Prodigy 80 points

Thanks Timothy, are you saying that the AGND and PGND are connected internally within the IC(LM5146) itself in the form of star connection? thanks,

0 Timothy Hegarty 7 months ago in reply to Sahil Gupta

TI__Guru 68757 points

The connection is made on the PCB under the IC. Both the AGND and PGND pins tie to the DAP copper.

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LM5146-Q1-EVM12V: AGND and PGND connection in EVM PCB