I have some basic Query While doing Decoupling Analysis of one of the board. Please help me out in resolving this query.

The scenario of my board is given below

VRM----(n1)---->FB----(n2)---->IC1

(n1)---->IC2

Where

n1=Power plane (1.375V)

n2=Power Plane (1.375V)

output Voltage of VRM = 1.375V

Ripple = 2.5%

IC1 is drawing ~ 3A of current from plane n2

I am doing the Decoupling Analysis of plane n1.

so I am assuming FB as one of the sink which is taking 3A of current from n1,

target impedance will come out to be only 19.462 mOhm below FB

My Query is am i doing it correctly by taking FB as one of the sink with 3A of current?

Do I need to make sure that the impedence graph is below target impedance even at the input of FB?

You won’t be able to achieve your target impedance goals if you keep the FB in your PDN. Typical values for a FB are:

· DC Resistance = 0.2 ohm

· Impedance @100MHz 120 ohm

With a 3A of current that flows through this FB, you’ll get a significant voltage drop across it.