FreeLists / si-list / [SI-LIST] Re: ESD solution on antenna output

["Sandor Daranyi" <sandord@xxxxxxxxxxxxx>]

Hello Ian,

There are ESD suppressor components offered for RF applications, but of cou=
rse they are highly dependent on the frequency, power, impedances etc. in=
volved. These parameters were not detailed in your post, so with a stab i=
n the dark for a small device with not very high frequency, there might b=
e a relevant device at=20
http://www.spkecl.com/htdoc/over-voltage-protector-ESD-Guard.htm or there a=
re other similar offerings from Littelfuse or Bussmann and others.

...but this wasn't your question.  You hinted at having a solution yourself=
, which involves removing the inductor.  I have to agree.  It's always tr=
icky to make a meaningful comment without knowing the details (and I'm no=
t an expert), but I don't see how the inductor could provide an ESD solut=
ion in that configuration, unless the frequency of transmission is very h=
igh and it is guaranteed that there is not much ESD energy at frequencies=
 approaching that.  Ever.

The noteworthy thing is that the most likely failure mode of the inductor i=
s open, which might keep the device operating, but it can then be (perhap=
s fatally) damaged by the next serious ESD event that comes along.

What actual (physics based) explanation has your colleague offered for the =
inductor, apart from that all ESD experts use it?  It suspiciously sounds=
 like it is something that is appropriate under some specific circumstanc=
es, and has then been applied because "experts do it".  People can get to=
uchy when they are asked about something they've done that they don't tot=
ally understand why...  Of course, we never see that on this forum!!!  ;-=
)

Regards,

Sandor Daranyi
Senior Design Engineer

Ian Barrett wrote:
> I am currently having a lively discussion with a colleague about an ESD
> problem we have encountered. The trouble is I don't think either of us=20
> know
> enough to be able to convince the other of our point of view.
>
> The product is a small radio transmitter that is very susceptible to=20
> an ESD
> spike applied directly to it's antenna. The design includes a small 
> inductor
> between the antenna output and ground. My colleague (the designer) put it
> there to try and alleviate any potential ESD problems. I have found 
> that I
> cannot solve the ESD susceptibility problem without removing it.
>
> He claims 'any ESD experts will tell you to place this inductor' and 
> wants
> me to try and find another solution to the problem. But I think the 
> inductor
> is making the situation worse by coupling the ESD spike onto the ground
> plane.
>
> Can anyone offer some theory to back up either argument?
>
> Ian.



------------------------------------------------------------------
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 technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu