[SI-LIST] Re: DC-DC converter Vs Signal Integrity
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: pakbazf@xxxxxxxxxx
- Date: Mon, 30 Apr 2012 19:42:36 -0400
Hi Don,
Yes, this concern is common with all topologies.
High efficiency requires low switching losses
and fast switching, so any parasitic inductance
and capacitance can ring more freely, producing
strong high-frequency ringing. Even if there is no
parasitic ringing on the switching edges, the loop
size around the high-current switches -even if done
carefully- may have enough area that the near-field
radiation becomes a problem. Converter circuits
can switch tens of amperes, the sensitive signal
lines run on miliamperes, which in itself creates
an approximately 60dB level of the required
isolation. If we have a 1% or 40dB 'crosstalk' target,
the isolation requirement becomes 100+dB.
You can find a couple of slides with illustrations
on this topic in the following publications at
www.electrical-integrity.com:
- Reducing EMI Noise by Suppressing Power-Distribution Resonances
Ansoft: EMI Control and PCB Power Analysis workshop, 22 August 2007,
Boston, MA and
- Panel discussion: What is New in DC-DC Converters?
DesignCon 2012, Santa Clara, CA, January 30 - February 2, 2012
Regards,
Istvan Novak
Oracle
On 4/30/2012 12:00 PM, Faraydon Pakbaz wrote:
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> Hi Istvan;
>
> Is this behavior common to all types of DC-DC converters (i.e. Buck, Bo=
> ost,
> etc) Topology? Is there any reference
> that I can find to discuss these situations? Thanks
>
> Regards;
>
> Don Pakbaz
>
>
>
>
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> Hi Bala,
>
> DC-DC converters have a tendency to produce high-frequency ringing on
> the main switching waveform edges, which can couple to nearby signal
> traces. It can affect any signal, not only reset. You need to select
> your converters carefully so that they do not produce too much noise an=
> d
> make sure there is no sensitive signal running too close to the
> converter. There are no specifications or generic rules that would wor=
> k
> for many situations; you need to look at this on a case-by-case basis.
>
> Regards,
>
> Istvan Novak
> Oracle
>
> On 4/30/2012 3:31 AM, bala wrote:
>> Hi Experts,
>> Does DC-DC converter noise creates any signal integrity problems othe=
> r
> than
>> normal power integirty issues?
>>
>> Especially,does it affect 'reset' signals.Please explain more if anyo=
> ne
>> came across such situation.
>>
>
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