Digital and Analog power Supplies

Hi,

I have the need to design Video ADC, on the chip im thinking about
using (ADV7181B) states the desired need to use seperate Analog and
Digital Power Supplies.

However I dont really want to have to supply another supply, as this
will complicate my design more than it need be.

The board I have is an FPGA board, so there will be the issue of noisey
power supply I suppose caused by digital logic.

What is the best way to use the power supply for my ADC but also has
the digital components in?

Any articles or information would be greatly recieved

Thanks

David

 

You don't need 2 power supplies, you just need to 2 connections. The
digital and analog will have seperate pins, you use seperate PCB tracks
from the pins to the decoupling capacitors. You may also like to use LC
filters, a small but low resistance inductor in series with the
supplies with caps on each side. You would probably take your analog
tracks up to the power supply rather than hanging them onto the digital
supply lines. What you are basically trying to avoid is having digital
circuits being supplied from the PCB tracks your analog circuits are
feeding from.

Many data sheets and app notes for analog/digital devices will give
examples, or you could just look "evaluation boards" for high end
chips, you will probably find the PCB layout in the online
documentation.