LMZM33603: Datasheet Grounding Recommendation

Grace Andersen

Part Number: LMZM33603

In the datasheet for this component, there is an analog ground and a power ground. The pin description for AGND says to not connect AGND and PGND, and that the connection is made internal to the device. Are there potential problems from connecting them? Is it possible to just use one ground for the device?

over 3 years ago

0 Samuel Jaffe over 3 years ago

TI__Mastermind 25590 points

Grace,

Yes, do not connect AGND to PGND on the layout. AGND for this device needs to be quiet. PGND has noise from the power stage so separating these pins (in this device) is advised. See the layout guidelines for a typical layout. Connecting them may introduce noise which can affect regulation and stability. Using just one GND would force the noise-sensitive circuitry to effectively use PGND for grounding which would introduce noise from the power stage into the noise-sensitive circuitry.

This is not the case for all devices so it's important to check the datasheet.

-Sam

0 Jim Gavin over 3 years ago in reply to Samuel Jaffe

Intellectual 920 points

Hi Sam,

Should AGND be considered an island that is isolated to the LMZM33603 and only used to connect to the Rt resistor and feedback resistors? Then PGND can be connected (same net) to circuit GND for the rest of the design, correct?

Thanks,

Jim

0 Samuel Jaffe over 3 years ago in reply to Jim Gavin

TI__Mastermind 25590 points

Jim,

Yes, see the layout example in the datasheet.

-Sam

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LMZM33603: Datasheet Grounding Recommendation