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Why so many FETs without SPICE models?

J

Joerg

Hurumph! Grumble, grumble ...

Today was frustrating. Requested several SPICE models for larger FETs,
all came back negative. From "Sorry, we don't have one" to "The
customers are encouraged to roll their own".

I mean, how do they engineer these things? Doesn't that sort of require
major SPICE sessions?
 
J

Jim Thompson

Hurumph! Grumble, grumble ...

Today was frustrating. Requested several SPICE models for larger FETs,
all came back negative. From "Sorry, we don't have one" to "The
customers are encouraged to roll their own".

I mean, how do they engineer these things? Doesn't that sort of require
major SPICE sessions?

Maybe you are in a dead-end portion of the engineering biz ?:)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food
 
J

Joerg

Jim said:
Maybe you are in a dead-end portion of the engineering biz ?:)

Not really. Right now it's power electronics, not exactly a dead-end market.
 
J

Jim Thompson

Sell the models?

Nobody is buying.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food
 
J

Joerg

Joel said:
The guys at Modelithics seem to do pretty well selling their models --
at work we have a copy of their "CLR" library, since it's a lot cheaper
to buy a copy than try to measure everything ourselves (particularly
when it's just, "well, this MIGHT be a useful part... but is it worth
half-an-hour to model it?), and we've found the models to be of very
good quality.

Unfortunately I suspect that they probably don't have models for the
particular transistors Joerg is after. They're more than willing to do
so on contract, of course, if there's some money around.

One of the vendors (IRF) actually wrote back that when there is enough
business in my case I might be able to convince a sales guy to get me a
model. Oh well, another company has already been financially impacted by
this old piece of American sales wisdom because I went to a competitor
that had models: "If you don't take care of your customer, somebody else
will".
 
J

Jim Thompson

The guys at Modelithics seem to do pretty well selling their models --
at work we have a copy of their "CLR" library, since it's a lot cheaper
to buy a copy than try to measure everything ourselves (particularly
when it's just, "well, this MIGHT be a useful part... but is it worth
half-an-hour to model it?), and we've found the models to be of very
good quality.

Unfortunately I suspect that they probably don't have models for the
particular transistors Joerg is after. They're more than willing to do
so on contract, of course, if there's some money around.

I suspect as electronics becomes further specialized, more and more
manufacturers will just contract with a place like Modelithics to
produce models rather than developing them in-house -- particularly any
manufacturer that isn't doing "cutting edge" products.

---Joel

I think it might have to do with product liability. The controls on
discrete device manufacture are looser than with I/C's. Thus the
reluctance to release models, particularly a collection of models
necessary to represent process corners.

So Joerg may be shooting himself in the foot if he relies too heavily
on the models provided by his "helpful" vendor.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food
 
J

Joerg

Jim said:
I think it might have to do with product liability. The controls on
discrete device manufacture are looser than with I/C's. Thus the
reluctance to release models, particularly a collection of models
necessary to represent process corners.

Simple fix: Put a disclaimer in there. That's what some companies do.

So Joerg may be shooting himself in the foot if he relies too heavily
on the models provided by his "helpful" vendor.

No, I design with plenty of margin. What I need to do is, for example,
simulate how deep and for how long I am diving into the SOA and such
when switching and sloshing "weird" loads around.

Anyhow, I'm fine. Looks like ON Semi might enjoy some new business while
others coulda, shoulda, but didn't.
 
J

Jim Thompson

Simple fix: Put a disclaimer in there. That's what some companies do.



No, I design with plenty of margin. What I need to do is, for example,
simulate how deep and for how long I am diving into the SOA and such
when switching and sloshing "weird" loads around.

Anyhow, I'm fine. Looks like ON Semi might enjoy some new business while
others coulda, shoulda, but didn't.

Proceed with caution. Awhile back I compared 8 models for the 2N7000
FET that everyone likes, and posted the results. Phenomenal variation
between vendors.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food
 
J

Jim Thompson

Proceed with caution. Awhile back I compared 8 models for the 2N7000
FET that everyone likes, and posted the results. Phenomenal variation
between vendors.

...Jim Thompson

Postscript...

I think what I'd do is roll my own low level model (like the crap
simplified model in the textbooks ;-), by taking data with a curve
tracer, then use the capacitances from the data sheet.

NOTE: This will NOT adequately model sub-threshold, or off-state
leakage. That requires a high level model and VERY fancy measuring
equipment.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food
 
J

Joerg

Jim said:
Postscript...

I think what I'd do is roll my own low level model (like the crap
simplified model in the textbooks ;-), by taking data with a curve
tracer, then use the capacitances from the data sheet.

I dun that :)

NOTE: This will NOT adequately model sub-threshold, or off-state
leakage. That requires a high level model and VERY fancy measuring
equipment.

That's the problem. Leakage isn't but I must spend some time in the
linear range with the PMOS device, including around the threshold. Peaks
to 100W.

<sweat beads forming on forehead>>
 
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