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PDN [Power Distribution Network]

Due to power consumption related to clock speed, tolerance of voltage fluctuation is getting shorter and shorter every year.
For example, recent power voltage is 1.5V, and tolerance of voltage becomes 0.075. (5% of 1.5V)

Because of voltage drops when consuming current from a power plane, capacitor helps to stabilize voltage fluctuation.
Putting capacitors everywhere on the board is an easy countermeasure, however, it is very costly and routing wires are more complex.
Therefore, considering location, quantity and capacitor value are most important to solving the problems.

Power Integrity Problems

 

PDN (currying current) from battery (VRM), IC consumes current. Less impedance in PDN is better. The latest chips uses low voltage, however, the current is getting higher. Switching current of IC runs like in this picture, voltage fluctuation drops at the same time. IP problems sometimes cause unmatched clock rhythm because of voltage fluctuation. To solve this issue, you need to place capacitors around critical IC. So far, engineers have been placing capacitors by their own experience or relying on engineer’s “hunch”, however, this is very costly. PIStream calculates the area where highly generate PI problems exist and shows visually where to place the capacitors.

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