ADS8528: ADS8528 PCB Layout: Analog and Digital Ground

joe lindula

Part Number: ADS8528

Hello, I am looking on page 47 of the ADS8528 datasheet.

On page 46, it states, "In case of separated ground areas, ensure that a low-impedance connection is
between the analog and digital ground of the ADC by placing a bridge underneath (or next to) the ADC."

So my question is, are the Red Vias in my graphic, are they tied together? Also, does it have to be ten vias?

Thank you

Joe

over 5 years ago

0 Dale Li over 5 years ago

TI__Mastermind 49515 points

Hi Joe,

They are not directly tied together, a single point short is a common practice for separated grounds. However, a solid ground plane is strongly recommended because keeping a low impedance connection may not be easy in many designs. All of our ADC EVM boards which were designed during past years used a solid ground plane. Please refer to the Inner Ground Layer in page 25 of ADS8568EVM-PDK User Guide.

Best regards,

Dale

0 joe lindula over 5 years ago in reply to Dale Li

Mastermind 6940 points

Hello, so are you saying it should look like this:

Here the blue vias would be tied to AGND.

Thank you for helping me.

Joe

0 Dale Li over 5 years ago in reply to joe lindula

TI__Mastermind 49515 points

Hi Joe,

From the image, yes. As I mentioned above, a solid ground plane is recommended if you are designing a new circuit board.

Best regards,

Dale

0 joe lindula over 5 years ago in reply to Dale Li

Mastermind 6940 points

Hello, I'm using an Analog Ground and Digital Ground. I tie the two grounds together where the power comes into the PCB. Does that sound okay?

Thank you

+1 Dale Li over 5 years ago in reply to joe lindula

TI__Mastermind 49515 points

Hi joe,

As I said, a solid ground plane is recommended, otherwise it may degrade the performance. You can check the user guide I highlighted. If you did not finish your design yet, I suggest you to change to a solid ground plane. If you have done it with separated grounds, I would suggest you to consider a solid ground design in the future.

Best regards,

Dale

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ADS8528: ADS8528 PCB Layout: Analog and Digital Ground