[SI-LIST] Re: Question on Common Mode Chokes and Unused Windings
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Erin.McPhalen@xxxxxxxxxxxxxxxxxxxxxxxxx
- Date: Mon, 09 Jul 2007 14:30:29 -0700
Erin:
a) Ground both sides - shorts the choke turning it into an air core
inductor.
b) Ground only one side - shorting the exterior side to your RF
reference would allow shunt of some HF junk through the parasitic
capacitance.
c) Leave the winding floating, simplest option and works.
d) Use a 2 winding choke. It's the right part for the job.
b) is the best choice IFF you can make a good bond to the RF reference.
Otherwise c) is the simplest and easiest way to go.
Steve.
Erin.McPhalen@xxxxxxxxxxxxxxxxxxxxxxxxx wrote:
> Hi
> We use a board level common mode choke, with 3 common mode windings. We
> currently only used 2 of the 3 windings. My question is what to do with
> the unused windings. I see 4 options here:
>
> a) Ground both sides
> b) Ground only 1 side
> c) Leave the unused winding floating
> d) Use a 2 winding choke(not actually an option for me)
>
> My concern is leaving an unintentional antennae on the board or interfere
> with the common mode rejection of the choke.
>
> Any insight would be greatly appreciated. Thanks in advance to any
> answers I get to this problem.
>
> Description:
>
> 3 Winding Common Mode Choke
>
> 1____(((((((((((____6
> 2____(((((((((((____5
> 3____(((((((((((____4
> =======
>
>
> Winding 1-6 and 2-5 are connected to signals leaving the EUT respectively.
>
>
> Winding 3-4 is unused, so I am not sure what would be the best treatment
> to this unused winding
>
>
> Erin
>
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