IR is insane
in [Design]
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From: John Fields on 19 Mar 2010 08:43 On Thu, 18 Mar 2010 20:26:08 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 18 Mar 2010 20:01:31 -0500, John Fields ><jfields(a)austininstruments.com> wrote: > >>On Thu, 18 Mar 2010 17:48:50 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Thu, 18 Mar 2010 19:37:49 -0500, John Fields >>><jfields(a)austininstruments.com> wrote: >>> >>>>On Thu, 18 Mar 2010 17:19:12 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Thu, 18 Mar 2010 18:02:27 -0500, Damon Hill >>>>><damon16ONE(a)comcast.not> wrote: >>>>> >>>>>>John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>news:cpb5q5p2013r34ainnmcrdfjml4ifvp03g(a)4ax.com: >>>>>> >>>>>>> Just got a short-form IR mosfet thing in the mail. >>>>>>> >>>>>>> They have a PQFN 5x6 mm package they rate at 104 amps. And a D2PAK >>>>>>> rated for 340 amps. >>>>>> >>>>>>Hmm. Define 'continuous'. (a >very< short pulse rating I'd believe) >>>>>> >>>>> >>>>>The flyer doesn't mention pulsing. The D2PAK datasheet pulsed current >>>>>rating is 1080 amps. >>>>> >>>>>http://www.irf.com/product-info/datasheets/data/irfs3006pbf.pdf >>>>> >>>>>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! >>>> >>>>--- >>>>Maybe they're talking power dissipation in the load with the switch >>>>saturated, like TI used to in the late 50's and early 60's. >>> >>>60 volts * 340 amps = 20,400 watts. So that ain't it. >>> >>>> >>>>In any case, if you don't believe it why don't you build something to >>>>prove your point instead of just flapping your gums, as usual? >>>> >>>>JF >>> >>>Are you willing to run a D2PAK fet at 375 watts power dissipation? Or >>>195 amps continuous drain current? >> >>--- >>It's not on me, John. >> >>You're the one doing all the bitching and moaning, so it's up to you to >>prove your point in the real world. >> >>It's not like you're financially strapped and can't afford to do it, so >>why don't you just put up or shut up? >> >>JF > >Heck, I don't need to experiment to show that 340 amps will blow a >dpak to hell at speed. --- You do if you want to find out, for sure, at what speed. --- >I'm an engineer, and can figure that out in >advance. --- But, being an engineer, you should realize that only testing in the real world will tell if you're right or not. --- >And all those flames and smoke and sparks would be downright >distasteful. --- If they proved your point, ISTM they'd be tasty morsels, indeed. But, will you do the experiment? I think we both know the answer to that one... JF
From: John Fields on 19 Mar 2010 08:51 On Thu, 18 Mar 2010 23:32:24 -0700, Muzaffer Kal <kal(a)dspia.com> wrote: >On Thu, 18 Mar 2010 15:58:08 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>Just got a short-form IR mosfet thing in the mail. >> >>They have a PQFN 5x6 mm package they rate at 104 amps. And a D2PAK >>rated for 340 amps. >> >>John > >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. --- Sanity, at last! :-) JF
From: John Larkin on 19 Mar 2010 10:07 On Fri, 19 Mar 2010 07:43:38 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Thu, 18 Mar 2010 20:26:08 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 18 Mar 2010 20:01:31 -0500, John Fields >><jfields(a)austininstruments.com> wrote: >> >>>On Thu, 18 Mar 2010 17:48:50 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Thu, 18 Mar 2010 19:37:49 -0500, John Fields >>>><jfields(a)austininstruments.com> wrote: >>>> >>>>>On Thu, 18 Mar 2010 17:19:12 -0700, John Larkin >>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>>On Thu, 18 Mar 2010 18:02:27 -0500, Damon Hill >>>>>><damon16ONE(a)comcast.not> wrote: >>>>>> >>>>>>>John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>>>>news:cpb5q5p2013r34ainnmcrdfjml4ifvp03g(a)4ax.com: >>>>>>> >>>>>>>> Just got a short-form IR mosfet thing in the mail. >>>>>>>> >>>>>>>> They have a PQFN 5x6 mm package they rate at 104 amps. And a D2PAK >>>>>>>> rated for 340 amps. >>>>>>> >>>>>>>Hmm. Define 'continuous'. (a >very< short pulse rating I'd believe) >>>>>>> >>>>>> >>>>>>The flyer doesn't mention pulsing. The D2PAK datasheet pulsed current >>>>>>rating is 1080 amps. >>>>>> >>>>>>http://www.irf.com/product-info/datasheets/data/irfs3006pbf.pdf >>>>>> >>>>>>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! >>>>> >>>>>--- >>>>>Maybe they're talking power dissipation in the load with the switch >>>>>saturated, like TI used to in the late 50's and early 60's. >>>> >>>>60 volts * 340 amps = 20,400 watts. So that ain't it. >>>> >>>>> >>>>>In any case, if you don't believe it why don't you build something to >>>>>prove your point instead of just flapping your gums, as usual? >>>>> >>>>>JF >>>> >>>>Are you willing to run a D2PAK fet at 375 watts power dissipation? Or >>>>195 amps continuous drain current? >>> >>>--- >>>It's not on me, John. >>> >>>You're the one doing all the bitching and moaning, so it's up to you to >>>prove your point in the real world. >>> >>>It's not like you're financially strapped and can't afford to do it, so >>>why don't you just put up or shut up? >>> >>>JF >> >>Heck, I don't need to experiment to show that 340 amps will blow a >>dpak to hell at speed. > >--- >You do if you want to find out, for sure, at what speed. >--- > >>I'm an engineer, and can figure that out in >>advance. > >--- >But, being an engineer, you should realize that only testing in the real >world will tell if you're right or not. 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. >--- > >>And all those flames and smoke and sparks would be downright >>distasteful. > >--- >If they proved your point, ISTM they'd be tasty morsels, indeed. > >But, will you do the experiment? > >I think we both know the answer to that one... Yes, but for different reasons. I *know* that 340 amps would incinerate a D2PAK mosfet, and you for some reason don't. John
From: John Larkin on 19 Mar 2010 10:16 On Thu, 18 Mar 2010 23:44:48 -0700 (PDT), George Herold <ggherold(a)gmail.com> wrote: >On Mar 18, 8:19�pm, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Thu, 18 Mar 2010 18:02:27 -0500, Damon Hill >> >> <damon16...(a)comcast.not> wrote: >> >John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in >> >news:cpb5q5p2013r34ainnmcrdfjml4ifvp03g(a)4ax.com: >> >> >> Just got a short-form IR mosfet thing in the mail. >> >> >> They have a PQFN 5x6 mm package they rate at 104 amps. And a D2PAK >> >> rated for 340 amps. >> >> >Hmm. �Define 'continuous'. �(a >very< short pulse rating I'd believe) >> >> The flyer doesn't mention pulsing. The D2PAK datasheet pulsed current >> rating is 1080 amps. >> >> http://www.irf.com/product-info/datasheets/data/irfs3006pbf.pdf >> >> 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 > >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 >175 Amps. > >George H. 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
From: John Larkin on 19 Mar 2010 10:19
On Thu, 18 Mar 2010 23:32:24 -0700, Muzaffer Kal <kal(a)dspia.com> wrote: >On Thu, 18 Mar 2010 15:58:08 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>Just got a short-form IR mosfet thing in the mail. >> >>They have a PQFN 5x6 mm package they rate at 104 amps. And a D2PAK >>rated for 340 amps. >> >>John > >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. 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 |