[SI-LIST] Fwd: Re: Re: Ferrite Beads on Differential Signal Lines?

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: "si-list@xxxxxxxxxxxxx" <SI-LIST@xxxxxxxxxxxxx>
  • Date: Fri, 12 Sep 2014 18:00:06 -0700


-------- Forwarded Message --------
Subject:        Re: [SI-LIST] Re: Ferrite Beads on Differential Signal Lines?
Date:   Fri, 12 Sep 2014 16:34:17 -0700
From:   steve weir <weirsi@xxxxxxxxxx>
To:     Joel Brown <joel@xxxxxxxxxx>



Joel, I am for doing what is needed. If the power rail is already quiet 
because it is very low Z then why add extra cost for no value?

If I need to insert loss without using a bunch of series impedance like 
a bead, then I bypass locally.  The capacitors that I really like for 
that are made by you know who and they excel at stripping off 
troublesome HF noise, without creating Z11 problems that beads do 
without load side bypassing.  If I have a need for more insertion loss 
than I can get with local bypass then I will manipulate etch first, and 
if that is not enough I will buy iron to supplant the bypass.  But the 
act of adding the iron often requires adding more bypass to take care of 
the Z11 inserted by the iron.

So:

Solve the problems that actually exist, and
Solve those problems by appropriate means.

If there isn't a problem to solve, it's time for a beer, not ferrite 
beads.  (Send them to little Gina.)
If there is a real problem to solve, and a ferrite bead is part of an 
appropriate solution then use it.


Steve.


On 9/12/2014 3:41 PM, Joel Brown wrote:
> Steve,
>
> I almost always see ferrite beads used for power in app notes for 
> clock generators / oscillators.
> Are you against using them there? If there is enough bulk and high 
> frequency bypass caps on the IC power pins then is it ok?
>
> Joel
>
>
> On Fri, Sep 12, 2014 at 3:09 PM, steve weir <weirsi@xxxxxxxxxx 
> <mailto:weirsi@xxxxxxxxxx>> wrote:
>
>     In the first case the decoupling capacitors satisfy the load where the
>     bead can't, whereas in the second case they are absent and the load
>     starves at medium to high frequency.
>
>     Steve.
>
>     On 9/12/2014 3:02 PM, Lucci, Christopher wrote:
>     > Mr. Weir -
>     >
>     > Can you further explain what you mean by not using a ferrite in
>     a power feed of a broadband amplifier (e.g. digital IC)?  How is
>     this different from #1 in the first list "As  part of a properly
>     decoupled high insertion loss filters."
>     >
>     > Not sure I caught what you meant?
>     >
>     > Respectfully,
>     > C. S. Lucci
>     >
>     > -----Original Message-----
>     > From: si-list-bounce@xxxxxxxxxxxxx
>     <mailto:si-list-bounce@xxxxxxxxxxxxx>
>     [mailto:si-list-bounce@xxxxxxxxxxxxx
>     <mailto:si-list-bounce@xxxxxxxxxxxxx>] On Behalf Of steve weir
>     > Sent: Friday, September 12, 2014 5:30 PM
>     > To: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
>     > Subject: [SI-LIST] Re: Ferrite Beads on Differential Signal Lines?
>     >
>     > While often abused, ferrite beads are a tool that have
>     legitimate purposes.  What makes no sense is to either:
>     >
>     > 1) "Solve" a problem that doesn't exist, or
>     > 2) Solve a problem with inappropriate means.
>     >
>     > Ferrite beads are very useful in these sorts of situations:
>     >
>     > 1) As  part of a properly decoupled high insertion loss filters.
>     > 2) As components in EMI filters.
>     >
>     > Places where they should not be used, or at least not used alone:
>     >
>     > 1) As power feeds to broadband amplifiers.  (All digital logic
>     devices qualify as broadband amplifiers.)
>     > 2) In circuits where their low to medium frequency behavior of a
>     high Q linear inductor has not been fully considered.
>     >
>     > Unfortunately, there have been many times that people have
>     misused ferrite beads creating bigger problems than the beads were
>     intended to solve.
>     >
>     > The National Ferrite Bead Association reminds us:
>     >
>     > "Ferrite beads don't kill designs.  Lazy engineers do."
>     >
>     > Best Regards,
>     >
>     >
>     > Steve
>     >
>     > On 9/12/2014 8:15 AM, Lee wrote:
>     >> It makes no sense to put ferrite beads in any signal line.  How did
>     >> this get started?
>     >>
>     >> -----Original Message-----
>     >> From: Craig Francis
>     >> Sent: Thursday, September 11, 2014 4:11 PM
>     >> To: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
>     >> Subject: [SI-LIST] Ferrite Beads on Differential Signal Lines?
>     >>
>     >> SI-List,
>     >> I haven't seen any literature concerning using ferrite beads on
>     each
>     >> signal line of a differential pair.
>     >> Usually only a common-mode choke is used to reduce common-mode EMI.
>     >>
>     >> Can ferrite beads be used on a differential pair to increase
>     the the
>     >> rise time of the signal and reduce unnecessary high-frequency
>     content
>     >> that may radiate?
>     >>
>     >> The two ferrite beads would be sized to allow the bandwidth
>     necessary
>     >> for the differential signal's highest data rate.
>     >>
>     >>
>     >> Thanks,
>     >> Craig Francis
>     >>
>     >>
>     >> ------------------------------------------------------------------
>     >> To unsubscribe from si-list:
>     >> si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'unsubscribe' in the
>     Subject field
>     >>
>     >> or to administer your membership from a web page, go to:
>     >> http://www.freelists.org/webpage/si-list
>     >>
>     >> For help:
>     >> si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject
>     field
>     >>
>     >>
>     >> List forum  is accessible at:
>     >> http://tech.groups.yahoo.com/group/si-list
>     >>
>     >> List archives are viewable at:
>     >> http://www.freelists.org/archives/si-list
>     >>
>     >> Old (prior to June 6, 2001) list archives are viewable at:
>     >> http://www.qsl.net/wb6tpu
>     >>
>     >>
>     >>
>     >>
>     >> -----
>     >> No virus found in this message.
>     >> Checked by AVG - www.avg.com <http://www.avg.com>
>     >> Version: 2014.0.4765 / Virus Database: 4015/8184 - Release Date:
>     >> 09/09/14
>     >>
>     >> ------------------------------------------------------------------
>     >> To unsubscribe from si-list:
>     >> si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'unsubscribe' in the
>     Subject field
>     >>
>     >> or to administer your membership from a web page, go to:
>     >> http://www.freelists.org/webpage/si-list
>     >>
>     >> For help:
>     >> si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject
>     field
>     >>
>     >>
>     >> List forum  is accessible at:
>     >> http://tech.groups.yahoo.com/group/si-list
>     >>
>     >> List archives are viewable at:
>     >> http://www.freelists.org/archives/si-list
>     >>
>     >> Old (prior to June 6, 2001) list archives are viewable at:
>     >> http://www.qsl.net/wb6tpu
>     >>
>     >>
>     >>
>     >
>     > --
>     > Steve Weir
>     > IPBLOX, LLC
>     > 1580 Grand Point Way
>     > MS 34689
>     > Reno, NV  89523-9998
>     > www.ipblox.com <http://www.ipblox.com>
>     >
>     > (775) 299-4236 <tel:%28775%29%20299-4236> Business
>     > (866) 675-4630 <tel:%28866%29%20675-4630> Toll-free
>     > (707) 780-1951 <tel:%28707%29%20780-1951> Fax
>     >
>     > All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
>     > This e-mail may contain confidential material.
>     > If you are not the intended recipient, please destroy all
>     records and notify the sender.
>     >
>     > ------------------------------------------------------------------
>     > To unsubscribe from si-list:
>     > si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'unsubscribe' in the
>     Subject field
>     >
>     > or to administer your membership from a web page, go to:
>     > http://www.freelists.org/webpage/si-list
>     >
>     > For help:
>     > si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject
>     field
>     >
>     >
>     > List forum  is accessible at:
>     > http://tech.groups.yahoo.com/group/si-list
>     >
>     > List archives are viewable at:
>     > http://www.freelists.org/archives/si-list
>     >
>     > Old (prior to June 6, 2001) list archives are viewable at:
>     > http://www.qsl.net/wb6tpu
>     >
>     >
>     >
>     > ________________________________
>     > The information contained in this message may be confidential
>     and legally protected under applicable law. The message is
>     intended solely for the addressee(s). If you are not the intended
>     recipient, you are hereby notified that any use, forwarding,
>     dissemination, or reproduction of this message is strictly
>     prohibited and may be unlawful. If you are not the intended
>     recipient, please contact the sender by return e-mail and destroy
>     all copies of the original message.
>     >
>
>
>     --
>     Steve Weir
>     IPBLOX, LLC
>     1580 Grand Point Way
>     MS 34689
>     Reno, NV  89523-9998
>     www.ipblox.com <http://www.ipblox.com>
>
>     (775) 299-4236 <tel:%28775%29%20299-4236> Business
>     (866) 675-4630 <tel:%28866%29%20675-4630> Toll-free
>     (707) 780-1951 <tel:%28707%29%20780-1951> Fax
>
>     All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
>     This e-mail may contain confidential material.
>     If you are not the intended recipient, please destroy all records
>     and notify the sender.
>
>     ------------------------------------------------------------------
>     To unsubscribe from si-list:
>     si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'unsubscribe' in the
>     Subject field
>
>     or to administer your membership from a web page, go to:
>     http://www.freelists.org/webpage/si-list
>
>     For help:
>     si-list-request@xxxxxxxxxxxxx
>     <mailto:si-list-request@xxxxxxxxxxxxx> with 'help' in the Subject
>     field
>
>
>     List forum  is accessible at:
>     http://tech.groups.yahoo.com/group/si-list
>
>     List archives are viewable at:
>     http://www.freelists.org/archives/si-list
>
>     Old (prior to June 6, 2001) list archives are viewable at:
>     http://www.qsl.net/wb6tpu
>
>
>


-- 
Steve Weir
IPBLOX, LLC
1580 Grand Point Way
MS 34689
Reno, NV  89523-9998
www.ipblox.com

(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax

All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
This e-mail may contain confidential material.
If you are not the intended recipient, please destroy all records
and notify the sender.





------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List forum  is accessible at:
               http://tech.groups.yahoo.com/group/si-list

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts:

  • » [SI-LIST] Fwd: Re: Re: Ferrite Beads on Differential Signal Lines? - steve weir