Question

The chip-size of a cpu is 15mm x 25 mm. Its clock frequency is 300 mhz and it operates at a supply voltage of 3.3v. The length of the clock routing is estimated to be twice the circumference of the chip. Assume that the clock signal is routed on a metal layer with a width of 1.2m and that the parasitic capacitance of the metal layer is 1ff/ m2. What is the power dissipated due to the clock signal?

Answer 1

Time (in seconds) -→

(1) 2:1:2

Answer 2

Answer:

The power dissipated because of the clock signal is $627 \mathrm{~mW}$.

Explanation:

Given:

• Dimensions of chip-size $=15 \mathrm{~mm} \times 25 \mathrm{~mm}$
• Clock frequency $=300 \space\mathrm{mhz}$
• Supply voltage $=3.3v$
• The length of the clock routing is twice the circumference of the chip.

We have to assume that the clock signal is routed on a metal layer with a width of $1.2m$ and that the parasitic capacitance of the metallic layer is $1 \mathrm{fF} / \mu \mathrm{m}^{2}$.

Total capacitance, $\quad C =4(15+25) \times 10^{3} \times 1.2 \times 1 \mathrm{fF}=192 \mathrm{pF}$

For clock signal, $\quad \alpha \quad=2$

Now calculate the Power dissipation:

$\begin{aligned}\mathrm{P} &=0.5 \alpha \mathrm{CV} 2 \mathrm{f} \\&=0.5 \times 2 \times\left(192 \times 10^{-12}\right) \times 3.3^{2} \times\left(300 \times 10^{6}\right) \mathrm{W} \\&=627 \mathrm{~mW}\end{aligned}$

Therefore, the power dissipated due to the clock signal is $627 \mathrm{~mW}$.