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Detecting floating node in schematic in Verilog-A code

vasug7

Hi,

I am designing a model of a semiconductor device which performs a specific function when one of the nodes is a floating. For my design, a floating node is something to which nothing is connected in the schematic window.

For example, 

As you can see in the figure, node2 is a floating node. 

I want to add an if statement in my Verilog-A code, such that the device model functions in a different way depending on the condition if the node2 is floating or not. 

I have tried to look it up in the Verilog - A reference manual, but couldn't find any useful information.

Any help will be appreciated.

Thanks.

  • There's nothing that really does this - but maybe you could check if there's any current flowing out of the pin? It does sound a bit of a strange requirement and without knowing the bigger picture it's hard to make a suggestion as to how to do it. Perhaps if you explained what you're actually trying to model an alternative could be proposed rather than this rather unusual requirement?

    Andrew.

  • in reply to Andrew Beckett

     Thanks, Andrew, for the suggestion. I also planned to solve this issue by sensing the current at the floating terminal (after connecting it to the ground). This will solve the issue, albeit but won't quite actually represent the real physical model.

    My requirement is something like this -

    There are some semiconductor devices, which perform functionally different depending on the condition if one of the nodes is connected to ground or floating. For example, there are internal physical effects taking place depending on the fact if the ions or electrons flow through the ground or are forced to tunnel via some mechanisms such as Channel hot electron injection etc (when the node is floating). 

    I want to model my device in such a way that these effects are taken into account. Which I thought could be done if Verilog-A could detect if something is connected to the node externally.

    I hope you understand where my problem emerges from.

    Thanks.

  • in reply to vasug7

    OK - but the real life circuit also doesn't "know" that the node is floating - so you need to model the electrical behaviour of the device. In a circuit simulator such as spectre, floating nodes are handled by providing a small conductance to ground which gives a leakage path to enable the node to be not completely floating (in real life there's usually some non-ideality which means there's a leakage path).

    Regards,

    Andrew.

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