IR is insane

John Larkin wrote in news: snipped-for-privacy@4ax.com:

Hmm. Define 'continuous'. (a >very< short pulse rating I'd believe)

--Damon

I wonder if any end user actually tries building the nucleated boiling heatsink to use those things at ratings.

Tim

-- Deep Friar: a very philosophical monk.

The flyer doesn't mention pulsing. The D2PAK datasheet pulsed current rating is 1080 amps.

The flyer claims 340 amps. The datasheet says 270 amps but "package limited" to 195. I don't believe any of them.

The datasheet also claims 375 watts power dissipation... in a D2PAK!

John

Are you willing to run a D2PAK fet at 375 watts power dissipation? Or

John

Maybe there was a simple typo in the information.

It may be a PQFN 5x6 meter package.

ve)

Wiki claims "hundreds of amps" for the secondary of the transformer inside those Weller soldering guns. So you got an easy source of amps there. Seems to me if the constriction in the copper bar that serves as the iron element gets hot, those tiny pins should get hot too?

Heck, I don't need to experiment to show that 340 amps will blow a dpak to hell at speed. I'm an engineer, and can figure that out in advance. And all those flames and smoke and sparks would be downright distasteful.

John

But nobody uses their soldering iron while submerged in nucleated boiling fluid.

In fact, it would be quite impossible to use -- I'd guess such an "IR-rated" soldering iron would be good for 10kW or more, continuous. And like the transistor, that doesn't mean you want to actually use it at that power level on a circuit board.

Tim

I am sure that you have seen the shrunken quarters.

Some pretty wild stuff.

http://205.243.100.155/frames/shrinkergallery.html

The only thing that actually matters is whether you can stay under the power curve of I^2*Rdson(T). At 1milliohm max 340 Amps gives you 115 W. You need to make sure to check the C/W rating of the package and cool it enough.

I wonder if they are dunking it and it's heatsink into liquid nitrogen. One figure in the data sheet showed the on resistance as a function of temperature. The minimum temp was -60 C with a current of

George H.

Wrong as can be. I *calculate* in advance if things will work, and almost exactly how they will work. The things I design are so complex that, if I depended on fiddling or breadboarding to see if they worked, or if I took a chance on even 5% of the important parameters in a system, I'd be out of business.

I only test parts if I believe that they are inadequately specified. I wouldn't test that IR part because I wouldn't buy it on principle, so there's no point.

Yes, but for different reasons. I *know* that 340 amps would incinerate a D2PAK mosfet, and you for some reason don't.

John

IR does insane things. The flyer I got spec'd the max current (340 amps!) and Rds-on different from the part datasheet (270 amps, or 195 amps "package limited")... all or which are preposterous for a dpak.

When people play games like that, I don't buy their parts.

John

Rds-on is spec'd as 2.5 mohms max at 170 amps, and will go up at higher currents as it self-heats. 340 amps would fuse the source lead.

There's no practical way to heatsink a D2PAK to dissipate 375 watts.

John

I have a vial of special gas which will conduct millions of amperes with only a few volts drop, But That's Not All, as an added bonus, it doubles as a switch, so you can connect your million-amp load in mere nanoseconds! How much you ask? For the low, low price of $2000!

I also sell bottled water...

Tim