Example Calculation of Power Strap Width with 6LM, 30% RAM, 20% Analog, Different Resistivities and Widths, 2W Core Power

Step 1: Calculate the voltage on the supply pad Vpad:

Vpad =	Vddmin-2×Ipad×(Rlead+Rbond+Rpad)
=	1.164 - 2 × 0.05 × (0.025 + 0.0125 + 0.05)
=	1.155V

Step 2: Calculate the reference power supply conductance G:

G =	7
	4×r(2)
=	7 / (4 × 0.07)
=	25 mhos

Step 3: Set out the values of j(n), k(n) and m(n) for each metal layer, and use these to calculate the value of L.

metal layer 1 2 3 4 5 6 j(n)  78%¹ 100% 100% 100% 100% 350%² conductivity coefficient k(n)  50% 100%  50% 100% 100% 200% power strap coefficient m(n)  50%  50%  50%  50%  20%  20% core area blocked

¹78% = .07/.09; ²350% = .07/.02

From which:

L =	j(1)×k(1)×(1-ps)×(1-(1-p)×m(1)) +
	j(2)×k(2)×(1-(1-p)×m(2)) +
	j(3)×k(3)×(1-(1-p)×m(3)) +
	j(4)×k(4)×(1-(1-p)×m(4)) +
	j(5)×k(5)×(1-(1-p)×m(5)) +
	j(5)×k(6)×(1-(1-p)×m(6))

We use the table below to iterate Step 3 to a value for L, Step 4 to a value for P(S) and Step 5 to a value for p, starting with p=0.

iter- ation	estimated p px‑1	Step 3 L	Step 4 P(S)	Step 5 new p px	delta p p (px‑px‑1)÷px
1	0.00%	7.801	0.203	9.83%	100.000%
2	9.83%	8.096	0.223	9.36%	-4.942%
3	9.36%	8.082	0.222	9.38%	0.224%
4	9.38%	8.083	0.222	9.38%	-0.010%
5	9.38%	8.083	0.222	9.38%	0.000%

Let us compare this solution with the previous one assuming that our metal-1 to metal-4 Vdd and Vss power straps are 5.5µm wide and metal-5 and metal‑6 straps are 11µm wide.