Thermal performance of IRLIZ44G vs IRLZ34 without heatsink

I'm trying to select the most 'versatile' N-Mosfet for my Arduino projects. Basically, the only three requirements are:

  • max current through the drain without heatsink requirement
  • logic level
  • form-factor of TO-220

So I ended up selecting between these two: IRLIZ44G and IRLZ34N. They main difference is Rds(on) which is 0,028 and 0,046 Ohms respectively and slightly different cases. If I understand it correct the first one uses the case without a built-in heatsink(?) I've found this article about MOSFET current raitings and made the following calculations:

So the Id max without heatsink (junction T=175C and ambient T=40C @5V) for IRLZ34 is 4,74 A and for IRLIZ44 is 6,26 A.

So IRLIZ44G has better results because of lower Rds(on) but since it's got no heatsink and much higher Rjc (3,1 vs 1,7 for IRLZ34), how can one use it at 30 A, won't it melt? Or there's a way to attach an external heatsink?

Which of these two FETs make more sense as versatile one for Arduino for powering loads of 12-24V with max current with and without a heatsink? So far IRLIZ44G seems to be a winner, but I don't get if one can attach a heatsink to it.

Thanks in advance :)

It's just isolated by the plastic casing. It will be a good thermal conductor, so you just mount it to a heatsink like you would for an exposed drain tab. It just eliminates the need to isolate it by other means for multiple components on the same sink

You want a much lower Rds for those kinds of currents. Pdissipated = IxIxR, so 30A x 30A x .028 ohm = 25.2W, smoking hot without a regulator.

A part with .004 ohm Rds =30*30*.004 = 3.6W. Still need a regulator, but not nearly as big. http://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOI510/785-1487-1-ND/3603498

This one might do better even, .0012 to .0016 ohm Rds, depends on how long the 30A is for, and you're going to have to get that 5V gate voltage applied nice & crisply http://www.digikey.com/product-detail/en/infineon-technologies/IRL40B209/IRL40B209-ND/5683946