ahhh another good idea Boncuk, copper trace. now it seems like the next thing undersized would be the leads coming off the Mosfets. i know they are rated for it, but it just seems to me that there has to be a better solution to my problem. i mean so far i need omething that has the ability of a high amp relay, but does not require a substantial draw
Hi browningbuck,
keeping the copper traces to the best achievable length reduces the trace resistance to a great deal. Of course it's impossible to route a trace of 1/5" thickness to the pad of a TO220 package, which requires reducing the trace width around the component pin.
Here are some numbers based on 1 oz copper weight, ambient temperature 30deg/C, total trace length 40mm (1.57") and 50A current flow (resistance values rounded to the nearest tenth):
trace width 5.08mm (0.2"), R=4.2mΩ, voltage drop=213.6mV, see remark*)
trace width 7.5mm (0.295"), R=2.8mΩ, voltage drop=144.7mV
trace width 10mm (0.394"), R=2.1mΩ, voltage drop 108.5mV
If those values seem too high you might either use PCB-material with 2 oz copper weight or a double sided 1 oz board.
The example shows 3.81 mm trace width for the TO220 package and 5.08mm for the TOP3 package.
Maximum total trace length is 20mm (10mm for a single trace)
* Remark: Although the value seems to be low the power dissipated in the trace is 10.68W.
Boncuk