[SI-LIST] Re: Measure ESD induced noise
- From: steve weir <weirsi@xxxxxxxxxx>
- To: chen_jinhua@xxxxxxx, "'Istvan Novak'" <istvan.novak@xxxxxxx>
- Date: Fri, 26 Aug 2005 06:51:36 -0700
Jinhua, have you taken measures to attenuate cable pick-up? I suspect you
are seeing a resonance with your measurement set-up.
Steve.
At 09:29 AM 8/26/2005 -0400, chen, jinhua wrote:
>Istvan
>
>I did those reference measurements. I also did the reference measurements
>with a cap, which has the same size and value as the on board decoupling
>caps. I expected the reference noise with cap should be bigger than the
>reference noise with short. Because cap impedance is always higher than
>short. But the result is opposite. Reference noise is bigger with short. In
>general, both reference noises (background readings) are much smaller than
>the real noise.
>
>Thanks!
>
>Jinhua
>
>-----Original Message-----
>From: Istvan Novak [mailto:istvan.novak@xxxxxxx]
>Sent: Friday, August 26, 2005 8:48 AM
>To: chen_jinhua@xxxxxxx
>Cc: si-list@xxxxxxxxxxxxx
>Subject: Re: [SI-LIST] Measure ESD induced noise
>
>Jinhua,
>
>There are reference measurements you can take: whether
>it is active probe or coax, solder both pins (signal and
>ground) to the ground point only. With active probes,
>make sure the position and orientation of probe head is
>the same that you have in subsequent measurements.
>
>You will find that active probes, passive probes and
>direct coax connections alike pick up noise from the
>nearby noise sources to varying degree. You have to
>use the connection, which gives a background reading
>comfortably lower than your measured data trace with
>your real connections.
>
>Regards
>
>Istvan Novak
>SUN MIcrosystems
>
>chen, jinhua wrote:
>
> >Hi, All
> >
> >I want to measure the ESD induced noise on the power and ground planes.
> >First thing I need to make sure is that the probe itself did not cause any
> >inaccuracy.
> >
> >Two different type of probes were used:
> >1.) high impedance single ended FET probe. Signal pin solder to power side
> >of decoupling cap, and ground pin soldered to ground side of cap.
> >2.) high impedance differential FET probe. '+' pin solder to cap power, and
> >'-' side solder to cap ground.
> >
> >I calibrated method 1 with a same size cap soldered on probe pins, but the
> >cap was not mounted on the board. Probe was placed on the same point as
>real
> >measurement.
> >
> >Are those two methods are valid way to measure the ESD noise?
> >
> >The results from two methods had some differences. Method 1 measured bigger
> >noise. The noise switching with 1 - 2 ns period and ~ 10 V swing in the
> >beginning, then decay to zero in about 100 ns. Method 2 had similar period
> >and 6 - 7 V swing, then decay to zero. But it had a wide pulse (50 + ns)
> >after the high frequency switching noise. I don't know how to interpret the
> >data.
> >
> >Thanks!
> >
> >Jinhua Chen
> >EMC Corp.
> >
> >
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