Constraints in routing analog and digital traces

[taring77]

Analog And Digitial

Hi all
what do i look out fr if i'm going to route digital and analog traces ?
any constraints to look out for??
thanks
Taring

 

[CDRCDR]

Analog And Digitial

Be sure whether your analog ground is separated from your digital ground.

If high speed,say a few hundered MHz or Multi-GigaHerz,you also need to be careful of the signal integrity

 

[andy1]

Re: Analog And Digitial

Be sure whether your analog ground is separated from your digital ground.

If high speed,say a few hundered MHz or Multi-GigaHerz,you also need to be careful of the signal integrity

If your signal in the digital and analog domain are completely isolated using transformer or optocoupler, then the digital and analog ground can be isolated.

But if the analog or digital signals are not completely isolated, which mean they are connected together at some place, then the grounds of the two domain HAS to be joined at some place. There are ways to do this to minimize the cross-talk although its hard for me to describe how it can be done in a few words.

Check out this book. It has a very good chapter on this.

Printed Circuit Board Design Techniques for EMC Compliance : A Handbook for Designers (IEEE Press Series on Electronics Technology)

 

[eziggurat]

Re: Analog And Digitial

There is a good article in the EMC and Compliance journal on Advanced PCB design and layout for EMC. You could possibly browse that online. They suggest using one ground plane for digital and analog using the stiching process.

Added after 24 seconds:

There is a good article in the EMC and Compliance journal on Advanced PCB design and layout for EMC. You could possibly browse that online. They suggest using one ground plane for digital and analog using the stitching process.

 

[kobik]

Re: Analog And Digitial

it depands on your application
analog - video, rf, dc/dc, audio ...
digital - high speed/ low speed

in general you can use one GND plane and seperat the
analog from the noise digital when you layout.

video or other sensitive analog circuits needs more care

 

[EEHardware]

Analog And Digitial

If you route Audio and Video Digtal and Analog,you must seperat the GND,i think it is the most imponent thing

 

[kobik]

Re: Analog And Digitial

saperate the ground plane is not so simple

if you tall us the application we will able to help you

 

[Rame]

Re: Analog And Digitial

Hi,

You can find lots and lots of article related to above topic if you google.Analog functional block need to be isolated from the digital part,if you using optocoupler then it is much easier to keep the parts either side and with proper isolation,this details can also be seen in the optocoupler datasheet(if u have using any!).

If you would tell us about the application of ur design,then probably we might suggest more information on that.Just say Routing guidelines for analog and digital in the address bar in the google search engine,you will end up seeing plenty of links,good luck.


Regards

Ramesh

 

[cyberrat]

Analog And Digitial

IMO.

Separating the "ground" is not the important issue, but separating the "signal return" paths is.

If you have a noisy/high current track, ensure that it has a good return path along to where it came from.

Return current will take the easiest path back to it's source, so don't cross A/D signals & returns etc.

You can still have a single ground plane layer, with minimal breaks in it if you do this.

If you keep that in mind when laying out the board, it should work lots better under EMC tests etc.