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In this image, the source 3.3V, which is going to three loads(U1,U2,U3), that consumes current of 2A,0.5A and 1A respectively,
As the total current is 3.5A.
Lets consider allowable ripple,
U1-2%
U2-3%
U3-5%

Then calculating targeting impedance,

z=(3.3*0.02)/3.5 = 18mE

Here I have taken the minimum allowable voltage ripple in the rail and the total current in it. Whether this method is correct. Or I need to calculate target impedance for three loads individually and do decoupling analysis. Like, U1-(3.30.02)/2 = 33mE, U2-(3.30.03)/0.5 = 198mE, U3-(3.3*0.05)/1 = 165mE Whether this procedure is correct?

Kindly clarify me, how to do decoupling analysis for this individual loads?

Selva97
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    What is an 'E'. What other things are you assuming? – Neil_UK Nov 05 '22 at 09:14
  • Total current doesn't matter, because DC isn't ripple; you need the maximum (worst case) change in current, perhaps in terms of step response (e.g. if this is a CPU or radio, perhaps it switches on and off abruptly), or if periodic, then at what frequencies. – Tim Williams Nov 05 '22 at 10:08
  • E is nothing but ohms. So how will you do decoupling analysis, if single power rail is connected to multiple load IC's – Selva97 Nov 05 '22 at 10:56
  • What's the maximum step load change, in Ampere? And what's the reaction time of your buck converter (time from load change to regaining regulation)? – Jonathan S. Nov 05 '22 at 13:10
  • I just need to know the correct steps to do it. – Selva97 Nov 05 '22 at 14:42

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