[SI-LIST] Re: Ferrite bead in ground path
- From: 李晖 <lihuizju@xxxxxxxxx>
- To: prashant.jaiswar@xxxxxxxxx
- Date: Sat, 22 Dec 2012 08:44:08 +0800
In my opinion, the FB is used to isolate different power supply and ground,
such as analog power and digital one.
Prashant Jaiswar <prashant.jaiswar@xxxxxxxxx>编写：
>I think the first question is to be shot to your MCU vendor,in the first place
>why the FB has been introduced onto the power supply? For any PSU design
>onboard, the basic requirement is to have minimised power plane impedance for
>the required frequency decoupling. Having FB onto the PSU line will introduce
>increased impedance for the desired frequency of operation.
>
>Sent from my iPad
>
>On 21-Dec-2012, at 11:31 PM, Hithesh <hitheshn@xxxxxxxxx> wrote:
>
>> 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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