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

It has:

  • AVDD
  • AGND
  • DVDD
  • DGND

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?

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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.

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  • \$\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

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.

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  • \$\begingroup\$ @thomas O check out this question: electronics.stackexchange.com/questions/7535/… \$\endgroup\$ – Mark Feb 2 '11 at 18:29
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    \$\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

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