[SI-LIST] Re: Current sense resistors and power integrity

Mikhail, what you need to do is maintain a low enough impedance on the 
load side.  The resistor / etch drawbridge or other method will 
introduce a substantial inductance that you will need to compensate for 
with a suitably low inductance capacitance on the other side, that also 
does not resonate with the inductance in your signal frequency range.

What I would recommend you do if you can is place your current sense 
back at the VRM, and then measure with your chip of interest at 
quiescent versus active.  The quiescent on most FPGAs and DSPs can be 
made pretty small.  This way you don't need extra parts in your bypass 
network, and you won't starve your parts.

Steve.
Mikhail Matusov wrote:
> Hi all,
>
> Is that a really bad idea to insert a small current sensing resistor, e.g. 3 
> mOhm, followed by a bulk capacitor in each power rail of a let's say a DSP 
> or a FPGA chip to be able to measure its power consumption?
>
>
> Thanks,
> =======================
> Mikhail Matusov
> Senior Hardware Design Engineer
> Square Peg Communications
> Tel.: +1 (613) 271-0044 ext.231
> Fax: +1 (613) 271-3007
> http://www.squarepeg.ca
>
>
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