[SI-LIST] target impedance profile

  • From: "ZHENGGANG CHENG" <zhenggang.cheng@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Sat, 24 May 2008 14:27:03 -0700

Hi all,
It seems many SI engineers are using the method described below to define
the target impedance profile for PSD:


Z(f) = 0.05*V_DC/I(f)                    or Z_target=0.05*V_DC/Imax(f)

Z(f)---target impedance profile at freq f;

Z_target---target impedanace at all freq;

0.05---allowed tolerance;

V_DC---power raill;

I(f) ---current profile;

Imax(f)---max I(f)---generallt 0.5Imax(t).

But this setup does not guarantee the overall noise is 5%.  All it does is
making sure noise at each of the frequency of interest is less than 5%.  In
time domain, the combined content has the possibility of bigger than 5%.

So is there a better way to define target impedance profile?

Thanks,

Zhenggang Cheng


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