# Power MOSFETS for 36V Motor Control

I have some basic understanding of MOSFETS. I was wondering if I could use MOSFETS to cycle this motor on/off for an engineering test.

• 36V
• 15A continuous current
• 550W
• 120 A inrush current on start up

I read through a “AN-7517.pdf” which I found at the www.onsemi.com site. They have some good resources. This is attached. I see in the 3rd guiding equation it asks for an inductance. Is the static motor inductance? Is there a way to estimate this or easily measure this?

Couple of questions:

1. How do I determine the Gate resistor Value
2. Is there a single MOSFET that will do the job, or will I need to put some in parallel?
-How does parallel MOSFETS work if i need to do this?
3)I found this MOSFET - http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FQP30N06/?qs=FOlmdCx%2bAA3GtR96ES2I6g==

It’s a 60V 32A rated MOSFET. THe data Sheet is attached as well. Would this one work?

AN-7517.pdf (97.3 KB)

FQP30N06L_datasheet.pdf (685 KB)

You’ll pop that MOSFET:

power = current x current x resistance

120 x 120 x 0.04 = 576W. Its only a TO220 package which can’t handle
that current since the leads melt. 4 in parallel would be more plausible.

However you might as well find a high-performance device in the first place,
2 milliohm on resistance is perfectly reasonable these days, get a few of those
in parallel driven by a MOSFET gate driver. Remember gate resistors if
driving > 1 MOSFET from a single driver.

For instance IRFS3107 (75V, 2.1milliohm)

At these power levels you must use a high current gate driver to reduce
switching losses in the device - a nice clean < 200ns switching time will
keep the kW’s at bay. MIC4422 will have enough oomph for a bunch of
MOSFETs.

[ oh yes, as for the inductive load, some big beefy dual schottkys on
a heatsink will be needed, something like 60V rated 2 x 20A in TO220
or TO247. ]

So you're saying I could use the arduino to run the MIC4422YM controller to switch a IRFS3107 FET. And I need a heat sink? what kind of heat sink for this configuration? It's not like the other transistor with the plate mounting.. http://www.digikey.com/product-detail/en/IRFS3107-7PPBF/IRFS3107-7PPBF-ND/1982966

What is the difference between an inverting controller and a non-inverting? Does it make a difference for my application?

Since this is an N-channel I would put it by the ground side, correct? Do I need to put a resistor to ground as well or will the controller make sure it is powered off?

Dissipation is calculated from the I-squared-R losses plus switching losses plus gate losses. Many many sites on the internet will cover that sort of thing.

The MIC4422 is not a controller, its a chunky gate driver that's needed to drive the gate properly hard for fast switching. Its available in inverting and non-inverting versions for convenience. If driving from a microcontroller its immaterial.

There are many possible MOSFETs out there, that's just one I happen to have a datasheet for lying around.

I gotcha! Thanks