Testing IRL540N IRL Mosfets

Thread Starter

adam450

Joined Mar 19, 2019
29
Just some random thoughts and confusion. I'm running a 10A solenoid pulsed and I was curious how some of these tiny TO-220 package mosfets are rated at ridiculous currents.

I was testing a IRL540N which is a pretty beefy mosfet, rated 26-36A depending on temperature, L for logic level. I was able to pull my 10A load if I gave it 6V-10V gate. But it's rated as logic level. Putting 5V to pull 10A and it burns up instantly.

At 5V the Rds or so must be too high and it gets destroyed. Also at 10A it should be pulling 4.4Watts. Rds spec = 0.044. So at the rated spec of 26A, that means this thing could pull 30W per their own spec (obviously with a heatsink). I just don't see how with any heatsink that this would work at the rated 26A. I have some high rated heatsinks (I think they are 10C/W or lower) attached as well during testing. Has anyone ever performed such high current with any of the IRL or IRF's? I suppose the 5V is just too low that all kinds of stuff happens that it blows up before a heatsink would matter, but sadly it says Logic level and does mention 5V Vgs in a couple spots. IRL/IRF's do work for me at higher gates, but I haven't investigated that over time or any good stats.

I've run STP16NF06L's at 5V gate and they are rated at Rds= 0.09 (9 Watts 2x what the IRL is pulling). Thats much higher wattage and I've used it with no heatsink pulsing it 100ms every second to 1/2 second for long periods of time switching it on and off. No issues.

So anyway maybe just the Infineon brand is just misleading? I just don't see how my STP holds up so much better than the Infineon IRL's, unless they are saying it CAN be driven at low gate, but at a much reduced current. Looking at their graphs it looks like I should be able to pull 10A with a 5V gate. STP is rated way lower and higher Rds. Confused why the STP holds up much better.

I also got these from a real supplier, not ebay.
 

Sensacell

Joined Jun 19, 2012
2,917
You make no mention of HOW you are driving the gate of these MOSFETS?

If your gate drive cannot deliver substantial current to quickly charge the gate capacitance, the device can experience huge power dissipation well beyond its limits while switching.


Post a schematic.
 

Thread Starter

adam450

Joined Mar 19, 2019
29
I'm driving it directly to a 5V power supply and connecting gate to +5V by hand very quickly. 6V works fine. My actual setup is a microcontroller with a drive transistor rated at 500mA. My gate has a drain resistor and turns off quickly. The IRL's just don't seem to like 5V that much or they are advertised as Logic level as long as your current is much lower, but the data sheet from what I look at suggests it will take that 10A at 5V gate.
 

ronsimpson

Joined Oct 7, 2019
1,630
The graph (high temperature) shows it should do 10A at 4V on the gate.
This graph shows 10A, 5VG-S and 1VD-S. I though it should be 0.65V D-S at 10A but ok. So 1V and 10A =10 watts and you don't have a heat sink. With no heat sink that 650C on the silicon. Even at 0.65 volts that more than 330C.
1626188924633.png
Get a lower Rds-on part. (higher current)
 

LowQCab

Joined Nov 6, 2012
1,307
"" Also at 10A it should be pulling 4.4Watts. Rds spec = 0.044. ""
I think You mean 0.44 Watts of Heat "Dissipation".

Touching a wire to a Transistor isn't exactly "Controlled-Conditions",
You need a clean, fast, On or Off, or tremendous heat gets generated instantly.

Many FETs are designed for High-Speed-Switching-Only, and
don't deal well with being used as a DC Switch.

Use one of these instead ................ IRL40B215
And mount it on a Heat-Sink first,
and make sure the Gate is grounded with an appropriate Resistor
before You go touching bare Wires to it.
The Gate must be Grounded under ALL circumstances, NO EXCEPTIONS,
otherwise it could be floating at any Voltage, and instant Blue-Smoke.
.
.
.
 

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Thread Starter

adam450

Joined Mar 19, 2019
29
I'll take a look at the IRL40B215. Looks like at 10A it has a much lower VDS so it may work.

" So 1V and 10A =10 watts "
Ah ok a lot of mosfets just show the Rds(on) graph, so I see where you had to work that graph to get it out. That graph still seems scary as even if I supplied 15Vgs, the wattage should still be the same roughly. It says 36A Continuous.

So to my original question really I'm just curious has anyone with the most massive of heatsinks, ever pulled 20+Amps continous out of an IR mosfet? Continuous means continuous to me so I understand it is a lot of power but " Many FETs are designed for High-Speed-Switching-Only ", it says 36A continuous, not pulsed. Just wondering if in any circuit, anyone has ever got an IR mosfet to hit something close to that continuous or not.

I went with the straight to power supply for investigative reasons only. Again doing it by hand at 6V works 100% no issues. 5V it dies. I can tap and release my keyboard button at 50ms, and with the wire should be the same. To make sure there was no voltage drop or other issues, I removed all circuitry and just worked with the mosfet. I tap and remove, quickly. I already stated I have a gate to ground, and that I have a massive heat sink on this thing. I have manually done the same with ST mosfets as well and it works fine. I can pulse STP16NF0L by hand or my microcontroller can pulse 100ms ON, 4x a second for hours. No heating issues or breakdown. That is rated at 0.09 Rds(on).
 

ronsimpson

Joined Oct 7, 2019
1,630
The RDSon is very dependent on temperature and gate drive.
Often the RDSon is "typical" not worse case. It is often cold or room temp. It is rated at the maximum gate voltage. It takes some effort to see that at 4V or 5V the resistance is higher. When hot the resistance is higher. And the worse case value is higher than typical. On the internet, looking for 0.044 ohms & 20A, but in real life we are seeing twice that resistance. The graph indicates 0.1 ohm at 4V GS.

There is also a chance the transistor is oscillating. I think the problem is really too much current and too little gate drive voltage and little heat sink.
 

Thread Starter

adam450

Joined Mar 19, 2019
29
Well at 5.5V I'm able to pulse the IRL540N, so that's good. I'll see how well it holds up since I didn't want to implement a dc-dc boost converter to get a higher gate voltage. I'm going to try using some other mosfets though that have a better Rds rating.
 

Audioguru again

Joined Oct 21, 2019
3,828
A Mosfet has a datasheet with minimum and maximum written specs and a graph for typical ones that a minimum or maximum one cannot do.
I was also going to mention an ebay counterfeit one.
 

LowQCab

Joined Nov 6, 2012
1,307
I think a lot more attention needs to be put on the safe-handling of MOS-devices.

The Gate is basically a very small "zero" Resistance Capacitor.
When the Gate is not Grounded, you don't have any idea of what the Gate-Voltage might be.
And it has a limited Voltage-Range, anywhere from ~+/-10V to ~+/-30V.

When the Humidity is low,
just walking across the Carpet in your House can generate ~thousands of Volts of Static-Electricity,
even ~50V of Static-Electricity can instantly destroy a MOS-Device.
And what's worse than that, is that the Gate can be "partially-damaged",
and still seem to work just fine, but it may have greatly reduced capacity.

MOS FET Transistors are not a "single" Transistor, they are usually made up of
several hundred really tiny Transistors, all paralleled together, and put into one Package.
This means that 3/4 of those tiny Transistors could be smoked,
and the FET may appear to still work perfectly,
it's just that now it may have only 1/4 of its original Current-Capacity,
and may have 4X its original Rds-On-Resistance,
so it will get HOT very easily, but may still work.

I always weave a fine strand of Wire between all 3-legs of any FET that I touch.
This wire remains there until the Board is completely populated and ready to test,
only then, do I cut the Wires off.

There's a really good reason why Semi-Conductors come in an Anti-Static-Bag and
usually with a piece of Conductive-Foam shorting-out all the Legs.
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Thread Starter

adam450

Joined Mar 19, 2019
29
I performed 2 live tests and calculated the Rds(on) to be 0.037 exactly for both tests by the way. That matches the datasheet. I only pulled 380mA and 747mA respectively. Obviously much lower amperage and heat, but the calculation seems good.
 
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