Re: Minutes from meeting on 2010.06.08 - solvers

What you say is correct. I was pondering systems of modeling
simultaneous equations in discrete time. Currently, real and wreal
ports can handle simple contributions. However, they can't handle
simple discrete devices, such as resistors or capacitors.

The resolution functions described in my article have enough power to
model such devices. However, modeling discrete devices requires a
knowledge of the Thevenin equivalent for all other devices on a port.
Most spice solvers don't explicitely calculate such values.

For example, a resistor model has two ports, P and N, and a resistor
value R. P is attached to some external circuits that driving a
Thevenin VPe (e is for external) and RPe. The resistor model will
drive port N with the Thevenin values (VPe, RPE+R). The value driven
onto the P port is similarly calculated from the external drivers on
the N port. For this to work, one must be able to ascertain the
external driver values. This is easily done in a discrete time
situation because one knows the resolved value on a port (which
includes external drivers as well as the internally generated driver).

However, this won't work when plugging into a matrix solver. The
matrix solver will present either a voltage or current. This could be
a problem the EDA firms might be able to solve.

But I was pondering an ability to pass parts of the matrix as a port
type, instead of a Thevenin equivalent. Could such a type system
interface better with continuous time solvers?

Regardless, I was just thinking out loud how one might improve the
plug and play ability.

Kindest regards,
Jim Lear

On Jun 11, 2010, at 8:13 PM, "Kevin Cameron" <edaorg@v-ms.com> wrote:

>> JL: That occurred to me. Matrix solvers don't have ports and drivers
>> they just have nodes. Possible to describe port or block in some
>> matrix
>> form?
>
> The analog (Verilog-AMS) equivalent of a driver is a contribution.
> You need a solver when contribution values are simultaneously
> dependent on each other i.e. for Kirchoff's current law to hold the
> sum of the current contributions needs to be zero. If the
> contributions are not simultaneously dependent then a solver is not
> necessary, e.g. if you have a bunch of currents into a resistive
> load, and you want the resistor voltage -
>
> analog V(R) <+ (I1+I2)*Res;
>
> - the voltage can be determined analytically and no solver is
> required if I1 and I2 have no dependence on each other or V(R).
>
> The D2A elements in Verilog-AMS convert drivers to contributions.
> D2As generating voltages are not generally simultaneously dependent
> on anything else (partly due to latency through the digital
> circuitry).
>
>
> Note: ports should have no significance in simulation (analog or
> digital), they are just part of the syntax of how you hook things up.
>
> Kev.
>
>
>

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