# I/O pad simulation : calculation of drive current ,pull-up and pull-down resistances

1. ## I/O pad simulation : calculation of drive current ,pull-up and pull-down resistances

What is drive current for a PAD and how to decide drive current for I/O PAD while doing characterization.Also how to calculate the pull-up and pull-down resistance for I/O pad cells.

Thanks

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2. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

Originally Posted by dileep4111
What is drive current for a PAD
The current which can be driven by the output buffer of the pad.

Originally Posted by dileep4111
how to decide drive current for I/O PAD while doing characterization.
While doing characterization you measure - you can't decide on your results (just if they are reasonable).

Originally Posted by dileep4111
how to calculate the pull-up and pull-down resistance for I/O pad cells.
Depends on requirements (customer's or yours).

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3. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

How should i characterize the drive current of pad. Currently i am using Spectre tool from cadance.
thank you

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4. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

Which type of pad? Analog or digital? Output only or I/O pad?

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6. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

Originally Posted by dileep4111
Again: Analog or digital? Provide its schematic!

BTW: Slowly I'm running out of endurance, if you're not even willing to provide the info necessary to be able to respond to your questions!

7. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

It is a bidirectional Digital PAD from TSMC

8. ## Re: I/O pad simulation : calculation of drive current ,pull-up and pull-down resistan

So why don't you simply have a look into the respective TSMC Standard I/O Lib Data Book? E.g. this one:
If you rightfully got the schematic and/or layout of the cell, you'd have access to it, too. There you can find the drive capabilities:
Pls. notice the correlation between a part of the cell name and its drive capability!

If you want to simulate: Enable the output, set a logic input voltage, measure the output current, either in short circuit mode, or into a known output load up to your requirement. Repeat this for the other logic input voltage.

Hope this helps!

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