I will dig out my Ott tonight and check that out!
The numbers I see from the Clemson calculator on near field shielding match my
experience ...
http://www.clemson.edu/ces/cvel/emc/calculators/SE_Calculator/nearfieldSE.html
Curt
Curt McNamara, P.E.
Engineering Consultant
612.305.0440 x248
www.npe-inc.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Ken Wyatt
Sent: Wednesday, March 15, 2017 12:11 PM
To: Curt McNamara <CurtM@xxxxxxxxxxx>
Cc: johnlinc@xxxxxxxxx; si-list <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Ground planes beneath power inductor/choke to isolate
high speed digital signal.
I agree distance is always important, but with today’s mobile devices, its
difficult to always implement adequately. Also, many on-board switchers
operate as high as 3 MHz. Above about 100 kHz, copper starts to work pretty
well to help confine the H-fields. See Ott, page 267 (Figure 6-24) for some
measured data (albeit for 3-mil, ~2-ounce copper). However, you can extrapolate
that for 1-oz copper (1.4 mils) might be 10 to 15 dB attenuation. For more
typical switching frequencies, we could easily be as high as 25 to 30 dB.
Cheers, Ken
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On Mar 15, 2017, at 9:26 AM, Curt McNamara <CurtM@xxxxxxxxxxx> wrote:
Inductors are used in switching power supplies to store energy in the form of
a magnetic field. This field increases and decreases over every switching
cycle. The resulting magnetic field external to the (magnetically shielded)
inductor can be minimized by careful layout.
However, copper is ineffective in reducing magnetic fields. Distance is your
best strategy.
Linear Tech has some good app notes on the topic.
http://cds.linear.com/docs/en/application-note/an139f.pdf
http://cds.linear.com/docs/en/application-note/an25fa.pdf
Curt
Curt McNamara, P.E.
Engineering Consultant
612.305.0440 x248
www.npe-inc.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of John Lin
Sent: Wednesday, March 15, 2017 1:01 AM
To: si-list <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Ground planes beneath power inductor/choke to isolate high
speed digital signal.
Dear SI gurus,
Could someone share experience on routing high speed digital signal
10GHz(layer 3), beneath inductors ( on the top layer)in switching power
circuit area with ground plane(s) (layer 2)for isolation?
What tools should be used to simulate induced noise coupling?
How many ground planes should be used to isolate noise induced by the
inductors?
Thank you for helps in advance.
Regards,
John Lin
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