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Altera_Forum
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13 years ago

PDN Tool Zh = Zs + Zv

Hello All! The PDN Tool shows the impedance between the decoupling network and BGA on the graph as Zh = Zvia + Zspreading, but if I leave the plane and BGA vias unchanged, the Zh value changes ...
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Altera_Forum
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13 years ago

Hi Steve,

Thanks for the reply, and the reference in the UG. I am working with an Arria V and will combine, for example, VCCL_GXB, VCCR_GXB and VCCT_GXB as they are all 1.15V. They all have F-eff at 70MHz, but different values of Zh:

VCCL_GXB Zh = 85mOhm

VCCR_GXB Zh = 30mOhm

VCCT_GXB Zh = 20mOhm

It makes a huge difference to the decoupling results depending on which one is chosen in the PDN tool, so in the end I have used the value for VCCR_GXB as this is the supply drawing the most current in my design.

It would be nice if Altera gave a bit more explaination about what the Zh values really are. They're obviously not just Zv + Zs.

Ken