Datasheet Error: ST STP24NF10

[kaboom]

So I'm building a 12V-19V boost converter for automotive laptop use, and noticed the heatsink getting hotter than expected.
I tuned my snubbering, and while I'm awaiting a better rectifier, it still seemed like too much temp rise. Snubbering it actually seemed to do little for this.

I also suspected the MOSFET, since there are some inconsistencies in the datasheet.
The heading implies the part is 5.5mohm, but other specs within the same datasheet suggest 55mohm, off by a factor of 10!

So I connected a spare 24NF10 directly to a power supply, source to the negative binding post.
It's actually the same 14V bench supply I'm using to test the laptop booster, so the gate was tied to the positive binding post via a test lead.
I used my 4-ohm audio dummy load, so 3.5A went thru the drain. Instead of the expected ~18mV across the MOSFET, I measured 180mV! Yep, that's a ~50 milliohm part!

See datasheet for details.
Note: the Digikey summary for this part shows 60 milliohms.
This correlates to what I measured, albeit under lower Ids.

[eccerr0r]

Re: Datasheet Error: ST STP24NF10

STMicro f**ked up their datasheet pdf, it doesn't agree with itself, Digikey is correct in this instance.

TBH I'd be wary of any MOSFET claiming less than 10mΩ Rdson, now I have to check all of them. *sigh*

[redwire]

Re: Datasheet Error: ST STP24NF10

To me looks like a datasheet typo for the RDS(on) spec. by a factor of 10!
But power mosfet datasheets are all hype and misleading, exaggerating things. Some specs I've seen have a *theoretical others measurements with a tiny pulse which makes more hype. Yeah 26A with a cold die.
You have to be really thorough when selecting them, manufacturers all give misleadingly low RDS(on) and unrealistically high ID.

OP's part for 2006 really low RDS(on) comes with high capacitance so I check that and this part is strangely low at Ciss 870pF. So a small die.
The graphs for RDS(on) Fig. 6 is 60-80mohm, and Fig. 10 shows it up +25% with temperature at 55°C, you have to factor in it's going to heat up.

[eccerr0r]

Re: Datasheet Error: ST STP24NF10

There is no such thing as a unicorn MOSFET, there is always something bad about each device. Whether or not you can live with the shortcoming is your job as the designer.

[redwire]

Re: Datasheet Error: ST STP24NF10

I think it's wading through fake specs on the datasheet full of marketing hype.
Most numbers are of the mosfet cold on an infinite heatsink, at 25°C for a tiny pulse "<300 μs pulses, duty cycle 0.5% max"
Oh you got 120A out of that little part? WOW I'LL BUY IT.
I find the SOA graph can say more in the end, but many are just a single pulse rated.