Re: gEDA-user: powermeter board, with less ground planes :-)

[Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx>]

Peter TB Brett wrote:
> On Friday 31 October 2008 20:22:59 Joerg wrote:
> 
>>>> Might want to rotate C11 and squeeze it in between R18/C12 so it's
>>>> closer to pin 4. But that really only matters if you expect lot of
>>>> RF from cell phones and stuff.
>>> Nope.  It's inside a metal box with all the circuit breakers.
>> That makes it pretty safe. But I did have a situation at a client where
>> this wasn't enough. Cell phone noise made it in via the cables. GSM
>> phones and BlackBerries were the worst for some reason. We fixed it by
>> switching to a device with clean CMOS inputs instead of BJT and
>> providing a nice little 0603 cap smack dab across the diff input, as
>> close as design rules would let us.
>>
> 
> Feed-through caps any potential use here?
> 

Yes, they certainly could have been. However, their mounting is rather 
cumbersome in production because they only work well if connected to 
stuff such as a tin can in an almost water-tight fashion. So we opted 
for a remedy right at the "victim" chip. This way they can simply mount 
the PCB, slide the can over, bolt that down and move on.

There are also nice (PCB level) EMI filter that reach way up into the 
GHz ranges from companies such as Murata. But when it comes to EMI I am 
a cheapskate and turn that 25c coin around and around until I have a 
0-10c solution ;-)

-- 
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
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