LT Devices, External Component Spice Models

For the switcher chip itself? Nope, that's secret. As are the programmable timer hooks in LTSpice that go beyond what regular SPICE can do. That's how they stay ahead of the competition ;-)

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Regards, Joerg

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Did I mention the switcher chip?

I need models for those passives. I'm rolling my own switcher ;-)

You do remember I was designing switchers back when I was a kid (and you weren't even a dream in your father's eye ?:-)

I just haven't done it in awhile, so my knowledge of modern passives is next to nil.

Yes and no. Great for LT-specific stuff. Not so great for pure analog at the device-level. ...Jim Thompson

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| James E.Thompson, CTO                            |    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     |

          Democrats are best served up prepared as a hash
           Otherwise the dogs will refuse to eat them :)

And my last switcher ran at 20kHz :-) Modern CMOS switches can run multi-MHz. ...Jim Thompson

--
| James E.Thompson, CTO                            |    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     |

          Democrats are best served up prepared as a hash
           Otherwise the dogs will refuse to eat them :)

Yep :-)

Yes, I remember that story when your boss came in, said "Sooo, you think this is bullet-proof, huh?" and then violently rocked the mains power switch.

I made my first switcher at around age 15. That was because I couldn't understand why fluorescent lamps in Europe would flicker several times until lit. Very aggravating when getting up at night. So, solder .. solder .. solder ... no more flicker, light were instantly on. I lost some of my respect for folks in the lighting industry that day :-)

Young buck to old buck: All you really need is inductance at around target current and DC resistance. T'is what the datasheet is for ;-)

If you want to cut it really close you'll have to measure saturation or use the 30% value from the data. SPICE lets you model inductor saturation. That's really all there is to it WRT switcher design. SRF and stuff generally doesn't matter because even a zippy 4MHz switcher running flat-out won't reach that.

Other than that there's just the usual, diode trr, capacitor ESR and such.

A client recently did some device level stuff and their IC design engineer was quite stunned what a free SPICE program such as LTSpice could do. At some point there will be situations where BSIM levels aren't supported of course but in general it's pretty good. They didn't have their design suite yet (but will soon).

--
Regards, Joerg

http://www.analogconsultants.com/

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I've burned the paint off powdered iron inductors in polyphase buck switchers, from pure AC core loss.

I actually invented the polyphase buck switcher, as I suspect many other people have.

John

I nearly always use ferrite. Cheaper. And no paint that could develop a tan and a stench. But one has to be careful because some of it can saturate wham-bam style. That would leading to an immediate PHUT ...

*POP* moment, resulting in what was in your FET mutilation picture.

At universities just about anyone invents the FFT and writes their own routines :-)

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Regards, Joerg

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You really ought to get your blood-flow and cholesterol checked out... you're showing signs of senility. It wasn't my boss. I've reminded you of that twice before :-)

Inductors aren't completely inductors. I'd like 'em characterized as complex elements when I'm pushing them along.

I'm quite capable of modeling saturation. I posted some years ago a model I devised that fits that nicely.

Mikey has put into LTspice just about every PSpice feature. All he needs for a first-class simulator is a good post-processor. ...Jim Thompson

--
| James E.Thompson, CTO                            |    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     |

          Democrats are best served up prepared as a hash
           Otherwise the dogs will refuse to eat them :)

Well, ok, someone else then. But he was an old buck compared to you :-)

What other factors are there? Some feng shui stuff in the inductor? As far as switchers are concerned inductors are no more complicated than a pair of hose clamp pliers.

So what's missing then?

Mike Engelhardt has probably brought more sales leads towards LTC than any other employee they ever had. There is absolutely nothing that beats the design confidence LTSpice can generate. If cost isn't super critical I always default to LTC for switcher chips. It is is critical one must roll yer own anyhow, or use a sub-$1 vintage chip.

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Regards, Joerg

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Nope. Ed Greenwood, at GenRad. He was about 10 years younger, and was a digital guy. He's been dead now for about 15 years... liver cancer... drank ~4 liters of Diet Pepsi every day... and weighed ~330# :-(

But he taught me that I'd better design _really_ good POR's :-)

Yep. ...Jim Thompson

--
| James E.Thompson, CTO                            |    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     |

          Democrats are best served up prepared as a hash
           Otherwise the dogs will refuse to eat them :)

Hi,

Here's a couple of ltpsice 200kHz switchers I've been working on (no complex inductor modelling though):

"

power boost/12v-14v-800watt-sync-boost.asc"

"

power buck/high power buck converter.asc"

Here are some nice high SMT inductors at mouser:

The synchronous boost IC is the LTC3813, anyone know of a similar chip that is cheaper?

cheers, Jamie