1
\$\begingroup\$

I am considering using a chip, but the datasheet is confusing me as it has several distinct power pins.

It has:

  • PLL_VDD
  • PLL_GND
  • AVDD
  • AGND
  • DVDD
  • DGND
  • DVDD_IO
  • DGND_IO

This is the chip.

How do I hook up each? Do I connect AVDD straight to DVDD, and what about PLL_VDD, and the ground pins? The suggested schematic seems to show them all connected to the same potentials (with different symbols for both types of grounds); from a cursory glance it doesn't mention anything about PCB layout. So how should I wire it up?

\$\endgroup\$
4
\$\begingroup\$

Divide your board into those discrete sections: PLL, Analog, Digital, and IO. Try to keep all of the copper (signal & power) for each section separate except where they require interconnect. Join the power to each sub-circuit only at near the power supply, within the sub-circuit and at chip when possible. Bypass each at the chip grounds with a cap or two (you might leave an extra footprint here for test).

You may find that the layout doesn't permit total separation of sub-circuits. If so, at least try to use a wider trace to supply the split and filter where necessary.

\$\endgroup\$
  • \$\begingroup\$ Separation of ground planes is a topic of holy wars... let's just say there are different reasons whether or not to just use one ground plane or have separate planes joined at one point. \$\endgroup\$ – Jason S Feb 3 '11 at 1:23
4
\$\begingroup\$

I'd filter the AVdd supply to minimise noise. The data sheet has a schematic on page 80 which shows all the connection details. Careful PCB design will be required, I wouldn't bother unless you have a lot of PCB design experience.

\$\endgroup\$
  • \$\begingroup\$ @thomas O check out this question: electronics.stackexchange.com/questions/7535/… \$\endgroup\$ – Mark Feb 2 '11 at 18:29
  • 2
    \$\begingroup\$ "I wouldn't bother unless you have a lot of PCB design experience." I disagree. I would bother because he will never learn if he never has the chance to try to do something like that and possibly fail at it. \$\endgroup\$ – Kellenjb Feb 2 '11 at 19:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.