[SI-LIST] Re: Separate GND for Analog & Digital
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: chris.mcgrath@xxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 23 Feb 2004 09:04:27 +0800
Dear Chris
I have done some simulation about the return path of VRM. There is a lot noise
in the return path of VRM.
The simulation about digital signal is too complex for there are too many
digital nets on the PCB. I have not done it.
Best Regards
Zhangkun
2004.2.23
----- Original Message -----
From: "Chris McGrath" <chris.mcgrath@xxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Friday, February 20, 2004 11:55 PM
Subject: [SI-LIST] Re: Separate GND for Analog & Digital
>
> I agree that the main issue is to isolate the return paths by connecting
> the grounds together at a single point and this is a pretty easy thing
> to do and you don't need additional ground planes to do it.
>
> That having been said, Zhangkun mentioned some CAD tools that can do
> simulations to test this. Forgive my ignorance, but would this be in
> the form of setting up digital aggressor nets to determine if they have
> any affect on the analog areas in this isolated ground area?
>
> Thanks,
> Chris
>
>
> > -----Original Message-----
> > From: Zhangkun [mailto:zhang_kun@xxxxxxxxxx]=20
> > Sent: Thursday, February 19, 2004 8:13 PM
> > To: maheshwari@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Separate GND for Analog & Digital
> >=20
> >=20
> > Dear Maheshwari
> >=20
> > We have come cross the simular problem. The critial point is=20
> > to prevent return path of digital signal disturbing the analog signal.
> >=20
> > In one of our PCB, there is too much digital noise in analog=20
> > signal. We have to repair it. How to seperate the ground=20
> > seemed to be the most important problem. One is to seperate=20
> > the ground and to connect the digital ground and analog=20
> > ground at one point. The other is not to seperate the ground.=20
> > In order to make sure that the product is OK, we made two=20
> > boards, seperated and not seperated. In the test, both boards are OK.
> >=20
> > It has nothing to do with seperating ground or not. Being=20
> > care of the digital return path is the most important. Some=20
> > CAD tools could do such simulation.
> >=20
> > I hope this will help.
> >=20
> > Best Regards
> >=20
> > Zhangkun
> > 2004.2.20
> >=20
> > ----- Original Message -----=20
> > From: "Maheshwari.P" <maheshwari@xxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Sent: Thursday, February 19, 2004 7:41 PM
> > Subject: [SI-LIST] Separate GND for Analog & Digital
> >=20
> >=20
> > > Hi All,
> > >=20
> > > I am designing boards which contain Audio and Video codecs.=20
> > I need to=20
> > > pass analog signal to the corresponding decoders without much noise.
> > >=20
> > > Is it better to have separate analog and digital GND?
> > > or
> > >=20
> > > Is it better to have a solid GND and have separate analog=20
> > and digital=20
> > > sections?
> > >=20
> > > Which of the either way will give better results in terms=20
> > of audio and=20
> > > video quality?
> > >=20
> > > Thanks in advance,
> > > Maheshwari
> > >=20
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