TMS320F2837xS Delfino layout- VSSA PIN

MARK PESACH

Intellectual 850 points

i am using the TMS320F2837xS LAUNCHPAD , and i want to design my own pcb .

i am using the 100 pin PZP package with power ground pad.

in the LAUNCHPAD there is no separation between analog and digital grounds , but i wish to make this separation .

i will be very grateful if some can help with this layout design:

does the VSSA and VSS are internally connected?

according to datasheet : VSS - Analog and digital ground -is the separation between analog and digital is made on the powerpad?

or do i need to connect my analog ground to the VSSA pins and not to the power pad?

best regards

MARK

over 10 years ago

0 Gautam Iyer over 10 years ago

Guru 192875 points

Hi Mark,

Check this document: www.ti.com/.../spraas1c.pdf

Regards,
Gautam

0 MARK PESACH over 10 years ago in reply to Gautam Iyer

Intellectual 850 points

hi Gautam thank you for your reply ,
i all ready went over this document, i still dont get it...
if i want to separate analog and digital grounds i need to tie my analog ground to VSSA? what about the power pad?

0 Joe Prushing over 10 years ago in reply to MARK PESACH

TI__Genius 17381 points

Hi Mark,
VSSA and VSS are not internally connected. If you want to keep them separate, VSSA should connect to your analog ground and the power pad to your digital ground.
Regards,
Joe

0 Devin Cottier over 10 years ago in reply to Joe Prushing

TI__Guru 60865 points

Hi Mark,

To add a little bit to Joe's response:

It is ok to either combine the grounds into a single plane, or to split the planes and then connect them at a single point (if they are split, they still should be joined at a single point).

More important is to make sure that the routing of the analog and digital signals are physically separated. One rule of thumb that is sometimes used is to create the split in the planes between analog and digital, route the analog and digital signal only over their respective planes, and then at the end to remove the split in the planes.

If you want to send your layout/schematics for a quick review at any point, you can send them to me (in .pdf, gerbers, or Altium format) at dcottier AT ti DOT com

0 MARK PESACH over 10 years ago in reply to Devin Cottier

Intellectual 850 points

hi

thank you very much for the detailed response!
now i think i got it.

best regards
Mark

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TMS320F2837xS Delfino layout- VSSA PIN