[SOLVED] Maximum Transient Current Calculation

[mishrashashi]

Hi,
I'm simulating my PCB for power integrity (IR Drop). I got a term "Target Impedance" (Ztarget)

Ztarget=[Voltage * (% ripple / 100) /Max Transient Current]

As per my consideration,
Voltage= voltage on a trace.
% Ripple is tolarance in voltage. (for example, 5V, 5% Ripple)

But I dont know, how to calculate Max Transient Current for a trace available on PCB. Please Help.

 

[loosemoose]

you could use the worst case peak current per rail : Ipeak = Pmax / VDD

you can estimate the transient current (rule of thumb : Itransient ~ 0.5 * Imax)

 

[mishrashashi]

Thanks Loosemoose,
I got the similar answer from other resources.
Maximum Transient Current:
A short-lived oscillation/decay in a system caused by a sudden change of voltage or current expressed as a function of time exponentially. The universal time constant formula is given by-
Change= (Final-start)(1-e-t/τ)
ITransient = Imax (1- e-t/τ)
Where,
τ= L/R
e= eular’s number ≈ 2.7182818
e.g. t=1 sec , τ= 1
Itransient = Imax(1- e-1)= Imax* 0.6321 ≈ 0.5*Imax