[SI-LIST] Re: ESD solution on antenna output
- From: "Charles Grasso" <cgrassosprint1@xxxxxxxxxxxxx>
- To: <sandord@xxxxxxxxxxxxx>, <Ibarrett@xxxxxxxxxxxxxx>
- Date: Mon, 2 Feb 2004 21:39:57 -0800
Hi - Typically lighning protectors for antennas use some sort of =
sparkgap/gas discgage tube to provide protection with low capacitance. I =
agree with the folks that advocate removal of the inductor..that will =
ring under ESD conditions and make the situation a lot worse!
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Sandor Daranyi
Sent: Monday, February 02, 2004 5:10 PM
To: Ibarrett@xxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ESD solution on antenna output
Hello Ian,
There are ESD suppressor components offered for RF applications, but of =
cou=3D
rse they are highly dependent on the frequency, power, impedances etc. =
in=3D
volved. These parameters were not detailed in your post, so with a stab =
i=3D
n the dark for a small device with not very high frequency, there might =
b=3D
e a relevant device at=3D20
http://www.spkecl.com/htdoc/over-voltage-protector-ESD-Guard.htm or =
there a=3D
re other similar offerings from Littelfuse or Bussmann and others.
...but this wasn't your question. You hinted at having a solution =
yourself=3D
, which involves removing the inductor. I have to agree. It's always =
tr=3D
icky to make a meaningful comment without knowing the details (and I'm =
no=3D
t an expert), but I don't see how the inductor could provide an ESD =
solut=3D
ion in that configuration, unless the frequency of transmission is very =
h=3D
igh and it is guaranteed that there is not much ESD energy at =
frequencies=3D
approaching that. Ever.
The noteworthy thing is that the most likely failure mode of the =
inductor i=3D
s open, which might keep the device operating, but it can then be =
(perhap=3D
s fatally) damaged by the next serious ESD event that comes along.
What actual (physics based) explanation has your colleague offered for =
the =3D
inductor, apart from that all ESD experts use it? It suspiciously =
sounds=3D
like it is something that is appropriate under some specific =
circumstanc=3D
es, and has then been applied because "experts do it". People can get =
to=3D
uchy when they are asked about something they've done that they don't =
tot=3D
ally understand why... Of course, we never see that on this forum!!! =
;-=3D
)
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=3D20
> 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=3D20
> an ESD
> spike applied directly to it's antenna. The design includes a small=20
> 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=20
> that I
> cannot solve the ESD susceptibility problem without removing it.
>
> He claims 'any ESD experts will tell you to place this inductor' and=20
> wants
> me to try and find another solution to the problem. But I think the=20
> 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.
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