IR is insane
in [Design]
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From: Tim Williams on 19 Mar 2010 11:11 "Robert Baer" <robertbaer(a)localnet.com> wrote in message news:QKGdnSW78tT5rz7WnZ2dnUVZ_uIAAAAA(a)posted.localnet... > ...in that case, i have some #30 wire rated at 1,000 amps and will > guarantee it or double your money back! 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 -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Muzaffer Kal on 19 Mar 2010 11:24 On Fri, 19 Mar 2010 07:19:50 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >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. > At those values the power dissipated by the part is "only" 73W. Actually the part is "package limited" to 195 A because bonding wires can't take it. >There's no practical way to heatsink a D2PAK to dissipate 375 watts. I am not sure how they come up with 375W but here is a simple calculation: The package's thermal resistance is 40 C/W when mounted on a 1 inchsq 1 ounce copper pad (I usually don't even have that much area but multi-layer helps) so if you limit junction to 150 C, the max one can do is 3.75W which comes out to ~38 Amps. -- Muzaffer Kal DSPIA INC. ASIC/FPGA Design Services http://www.dspia.com
From: John Larkin on 19 Mar 2010 11:36 On Fri, 19 Mar 2010 08:24:16 -0700, Muzaffer Kal <kal(a)dspia.com> wrote: >On Fri, 19 Mar 2010 07:19:50 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>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. >> >At those values the power dissipated by the part is "only" 73W. >Actually the part is "package limited" to 195 A because bonding wires >can't take it. > >>There's no practical way to heatsink a D2PAK to dissipate 375 watts. > >I am not sure how they come up with 375W but here is a simple >calculation: The package's thermal resistance is 40 C/W when mounted >on a 1 inchsq 1 ounce copper pad (I usually don't even have that much >area but multi-layer helps) so if you limit junction to 150 C, the max >one can do is 3.75W which comes out to ~38 Amps. 375/3.75 = 100. So it's practical to use this part at 1% of its specified maximum power dissipation! Maybe they just slipped two decimal points on the datasheet power dissipation, and one decimal point on the max current in the flyer. John
From: John Fields on 19 Mar 2010 12:05 On Fri, 19 Mar 2010 07:16:29 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >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. --- Oh, well, it's your loss... 60Vdss, Rds(on)max 2.5milliohms, 375 watts @25C Tc, it's a nice part. JF
From: langwadt on 19 Mar 2010 12:19
On 18 Mar., 23:58, John Larkin <jjlar...(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 think this has part of the long explanation as to how the come up with the numbers http://www.datasheetarchive.com/pdf/Datasheet-076/DSAE0035054.pdf -Lasse |