sheldon
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Paul,
There are a lot of different philosophies on this topic and the answer depends what you are trying to do. If you are just building a simple model to test an idea than you probably don't need power supply connections. However, if you plan to anything close to design, then you will need to add power supply pins. In fact, I would all the pins at all the levels. "Pin correct" behavior modeling is important for a couple of reasons. First, is is useful if you share models with other designers, in particular, system designers. System designers need to interface to the block so having all the pins and modeling them correctly are important. For example, is signal X active hi/active lo, is the output 2s complement/straight binary, ... Next, it will help you out during design for the same reason, that is, it will allow you verify all the modes of operation for a design. On some recent models, we included effects such as lock-out, if the power supply drops below a certain voltage the block stops working allowing us to model start-up. In addition, pin-correct models allow you to debug your testbenches and verification strategy before starting transistor level design. Debuggin at the transistor level is a pain, nobody wants to wait 5 hours for a simulation to complete only to find a testbench issue. Finally, pin correct means all the symobls and the design heirarchy are correct which again makes transistor level design al lot easier.
So if you are designing a channel filter for a Wireless application: Case I: what is the effect of open loop gain on the transfer function? don't need power pins Case II: Does the filter calibration algorithm work correctly? probably need power supply pins, that is, does the filter start-up, does the calibration block start-up, is calibration disabled when complete, ...
Sorry for the long answer, hope it helps, or at least stimulates some more discussion.
Best Regards,
Sheldon
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