power mesh calculation questions ??

[devop]

Here's power mesh calculation from a paper, but I'm not very clear about that,

Iblock= Pblock / Vddcore
 Current supply from each side of the block:
Itop=Ibottom= { Iblock *[Wblock / (Wblock +Hblock)] }/2 ---------(1)
Ileft=Iright= { Iblock *[Hblock / (Wblock +Hblock)] }/2
 Power strap width based on EM:
Wstrap_vertical =Itop / Jmetal
Wstrap_horizontal =Ileft / Jmetal
 Power strap width based on IR:
Wstrap_vertical >= [ Itop * Roe * Hblock ] / 0.1 * VDD
Wstrap_horizontal >= [ Ileft * Roe * Wblock ] / 0.1 * VDD ------------(2)


two questions here:
1, how does formula(1) comes out?
2, based on formula(1) , the vertical strap consume 10% vdd ir drop ,why don't count the Metal 1 IR drop together???

 

[vlsichipdesigner]

hi ,

my 2 cents

let me help you to understand the equations

V=IR
R = ρL/A = ρL/w*t, where ρ/t can be treated as Rs => Rs*H/w.
whereas A = width*thickness

Here you have to assume as Branch current.
Iblock*Rs*H/w / (Rs*H/w + Rs*W/w)
= Iblock * Rs *H/Rs (H+W) = Iblock *H/H+W

where H = height of the block, W = width of the block, w = thickness of metal
Itop = Ibottom = (Iblock*H/H+W)/2

hope it is clear,

myprayers,
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