Interesting Simulation Problem

Jim Thompson · 2014-03-23T00:13:41+00:00

Lots of bad-mouthing about simulation of circuits, but here's a real world problem for you... Suppose you have a circuit made up of 10,000 NMOS and 10,000 PMOS devices plus a few resistors, capacitors and PNP's thrown in to make an ANALOG circuit. Said ANALOG circuit goes in a medical-implant environment and, to conserve power, it is only turned on periodically, does its task, then goes back to "sleep" for an extended period of time. During this "sleep" period we want to ensure that only picoamps flow during the "sleep" interval, so we devise various disconnect and shorting devices that make sure everything is turned off. What is always worrisome to the designer is how to ensure all possible sneak paths are blocked, and that no nodes can FLOAT around and ultimately turn on something by chance (it's really easy to turn on an MOS device if its gate is floating). So the question... in simulation we hit the "sleep" switch and then check all nodes to make sure nothing is floating. Visually we can do that in simulation. In PSpice all nodes can be lit up showing the potential on each. The snag is PEOPLE... how do we make sure we have checked every node? More particularly, can anyone devise a way that we could automatically find floating nodes? I know the almighty Oz has declared simulation a crutch, but how do you really verify what I've described... at LEAST 30,000 nodes to check? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Mar 23, 2014 40 Replies

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John Fields 12 years ago

Well, I see some progress has been made in that your verbosity has decreased substantially, albeit still being bereft of worthwhile content. Perhaps another shot or two will convince you to shut the fuck up and rid us all of both problems. John Fields

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