[SI-LIST] Re: Ferrite bead in ground path
- From: Hithesh <hitheshn@xxxxxxxxx>
- To: garys@xxxxxxxxxxx
- Date: Fri, 21 Dec 2012 23:31:19 +0530
Gary,
The ferrite is between the MCU analog ground(GNDA) and the circuit
ground(not chassis ground). Majority of the components on the board are
digital(MCU, SDRAM etc). There's also a ferrite in the power section.
The MCU has 1.8V for analog circuitry (not ADC), probably PLL or some Vref
circuitry. I did a quick datasheet search, didn't get any details.
-Hithesh
On Fri, Dec 21, 2012 at 11:16 PM, Gary Stein <garys@xxxxxxxxxxx> wrote:
> Ground path between what? Beads between chassis ground and signal ground
> are frequently used for emi/esd suppression, ie keep external high
> frequency
> transients out of signal ground and to keep any ground noise from radiating
> from connectors shells and such. In such applications, chassis ground is
> not a signal nor power return path.
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Ken Wyatt
> Sent: Friday, December 21, 2012 11:43 AM
> To: hitheshn@xxxxxxxxx
> Cc: SI-List
> Subject: [SI-LIST] Re: Ferrite bead in ground path
>
> I've seen ferrites in series with the green wire safety ground wire.
> Otherwise, I wouldn't think you'd want an impedance in the signal OR power
> return path, unless you'd want to keep us consultants employed!
>
> Cheers, Ken
>
> Kenneth Wyatt
> Wyatt Technical Services LLC
> Woodland Park, CO
> ken@xxxxxxxxxxxxxxxx
> www.emc-seminars.com
> (Sent from my iPad)
>
> On Dec 21, 2012, at 10:14 AM, Hithesh <hitheshn@xxxxxxxxx> wrote:
>
> > I came across an old schematic that has ferrite bead in the ground
> > path. Is there any advantage of using ferrite bead in the ground path.
> > The general rule is to keep the ground path at low impedance.
> > -Hithesh
> >
> >
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