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How to find the Rise time & Frequency of the Controller Signal?

Sprak.11
Associate II

I Want To avoid Cross talk in PCB I want to know how to find the Rise time & frequency of the Signal?

& Where I can Get the Spice model of the Micro Controller(* In my case, I am using STM32L4R9ZT6)

4 REPLIES 4
TDK
Guru

You can find some signal characteristics in the datasheet under "Table 77. I/O AC characteristics", including rise times.

https://www.st.com/resource/en/datasheet/stm32l4r5vi.pdf

I don't think you'll find a SPICE model anywhere.

If you feel a post has answered your question, please click "Accept as Solution".

May I know what is the use of the capacitance & how to use that Speed?

can you please explain that Because I am not aware of that

0693W00000D1TP6QAN.jpg

TDK
Guru

Pin capacitance is nominal 5pF per table 75.

If you feel a post has answered your question, please click "Accept as Solution".

They are using capacitance here as a proxy for the type of load you have on the pin for the purpose of generating graphs/tests which can be put into the take. ie conditions to allow you to replicated the test, and get similar results.

The capacitance (resistance to change) present on your board is going to be a function of the traces, and what they are attached too, and how many things they are attached too. The SPEEDR setting on the IO Cell is effectively a slew-rate control, how aggressively the pin is driven high/low, and how much current (nee energy) the transistors can switch/transfer instantaneously.

ST might be able to provide a model of the IO Cell, you should check with the FAE responsible for your account.

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