Mosfet not switching on Due

I'm using FDP7030BL mosfet. Gate goes to pwm output on the Due and is receiving 3.3v. Drain goes to a diode then to the shield on an RCA jack that will power a 12v fan. Inside of the RCA gets a 12v source and connected to the other side of the diode. Source goes to ground. I never receive any voltage to the fan (or the drain). Will the mosfet work ok with only 3.3v gate?

TY!

https://www.digikey.com/product-detail/en/fairchild-on-semiconductor/FDP7030BL/FDP7030BLFS-ND/976591

Not quite sure how you have it wired, but it doesn't matter anyhow. The Vgs threshold is 3V, which means it barely starts to turn on at 3V. At 2.9V, it is fully off. You need a Vgs ON of 3V, which would mean the Vgsth would be somewhere less than 2V

TY.

If I'm using it as a switch with PWM coming from the output pin - wouldn't it be all on or off at the fan? So long as I have > 3V, it would activate the fan at full 12v capacity?

For wiring, I have 12v going to one side of the fan and the other side is connected to the drain. I have a diode between the fan wires.

https://www.digikey.com/product-detail/en/comchip-technology/1N4001-G/641-1310-1-ND/1979675

When the Gate gets 3.3v, the fan should get the full 12v right?

TY again!

This is the schematic I'm following.

http://hruska.us/tempmon/

fordfanboi: I'm using FDP7030BL mofset. Gate goes to pwm output on the Due and is receiving 3.3v. Drain goes to a diode then to the shield on an RCA jack that will power a 12v fan. Inside of the RCA gets a 12v source and connected to the other side of the diode. Source goes to ground. I never receive any voltage to the fan (or the drain). Will the mofset work ok with only 3.3v gate?

TY!

https://www.digikey.com/product-detail/en/fairchild-on-semiconductor/FDP7030BL/FDP7030BLFS-ND/976591

You wont measure any voltage at the drain unless there is a load connected. The way that I read your description, the motor is not yet connected. At present there is no load connected to the RCA connector that you are driving. Place a resistor across that connector and then you'll see it.

Also, be aware that you are operating very close to the worst case gate threshold voltage there. Your circuit will probably work for "typical" device parameters, but may struggle under worst case parameters.

What is the maximum load current going to be?

fordfanboi: If I'm using it as a switch with PWM coming from the output pin - wouldn't it be all on or off at the fan? So long as I have > 3V, it would activate the fan at full 12v capacity?

No. You are still right at the threshold voltage. Grab your voltmeter and see what you have across the blower leads.

You need a 5V signal on the gate to switch it on fully.

tinman13kup: No. You are still right at the threshold voltage. Grab your voltmeter and see what you have across the blower leads.

I agree it's poor utilization of that device tinman. However the op is driving a fan through an RCA jack, so possibly just a few hundred mA. That device will switch a low current (say 200 mA) even at 0.2 volts above the threshold (not shown on datasheet but I can calculate this indirectly from other the parameters - and using worst case rather than typical parameters too). Poor utilization of a 60 amp device though. ;)

You need a 5V signal on the gate to switch it on fully.

Again, it is if you need to efficiently control up to 60 amps. I suspect the load current here is going to be very much lower. Let me say that overall I agree with you though, he is operating WAY too close to the worst case threshold.

fordfanboi, if you can find an alternate mosfet with a worst case threshold voltage of 2.5 volts or even lower then it will make your circuit a lot more reliable. Either that or just use a BJT.

Awesome info - will try to track that down.

It is working now - turned out the issue was with the RCA connector. The positive side has 2 connections to the board and the ground has 1. I had tied the power into one of the 2 connections and it turned out that connection gets disconnected when the RCA male plug is inserted. Derp. I moved the power to the other side and the fan is now live.

Should be easy to swap in a better mosfet too. Thanks again!