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Input/Inout Pin Capacitance Attributes

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janthonym

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Hi all,

I'd just like some clarifications with some of the capacitance attributes for liberty (.lib) files.

I understand that the rise capacitance and fall capacitance attributes are the capacitance values for the input/inout pin for rising and falling waveforms. I also know that the capacitance attribute is the measured capacitance of the input/inout pin you are on and it is measured in the spice simulation.

I'd just like to clarify, so is the pin capacitance is measured at more of a stable waveform (not rising or falling)?

Thanks in advance!
 

janthonym

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Liberty files: [Input Pin] Capacitance, Rise/Fall Capacitance Ranges Attributes

Hi all,

I'm was trying to understand all aspects of the liberty file and I came across some questions.

I'm looking at the input/inout pin attributes - capacitance, rise/fall capacitance, rise/fall capacitance range and would like to know more about them. From what I understand, I know that the pin capacitance attribute is the measured capacitance that is measured directly in SPICE calculations and the rise/fall capacitance values/ranges are calculated based on the pin capacitance value for rising and falling waveforms.

I assume that the pin capacitance value is measured at the high/low levels of the signal whereas the rise/fall capacitance values are related to their respective edges, correct?

As a rule of thumb, do the capacitance and rise/fall capacitance values have to be within the rise/fall capacitance ranges? It makes sense that the rise/fall capacitance value has to be within the rise/fall capacitance ranges but what if I come across a (just) capacitance value that is outside of the rise/fall capacitance ranges?

Thanks in advance!
 

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