International Rectifier / Infineon IRF MOSFET are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for International Rectifier. IRF Transistor Datasheet, IRF Equivalent, PDF Data Sheets. MOSFET. Parameters and Characteristics. Electronic Component Catalog. 25 Aug Е Uses IRF data and test conditions. Source-Drain Ratings and Characteristics. Parameter. Min. Typ. Max. Units. Conditions. V(BR)DSS.
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Yes you want this, but how do you switch it off? I’ve done some more thinking, and have come up with something else; no idea if it’d work, but what the heck, throw it out there and see what sticks. That’s why most people just use packaged solutions.
I’m aware that the specified components may not be optimal and there are likely support components missing, but this is just to see if this could work in theory. I don’t understand hardly any of “5”and have only partially figured out the push-pull arrangement in “3”so I’m not sure of any of the supporting components in either circuit missing, in excess, mis-valued, etc. MarkT on Jan 30, It’s a tad pricey, but if this becomes a 2-chip solution So, I came up with again, “c” irf4950 a “common” approach and “e3” is my latest incarnation: While I appreciate learning more about the hows and whys of doing things these ways, at the moment I just need to get it to work – preferably as efficiently as possible while keeping discrete component count to a dull roar.
If4905 did a Google search on irv4905 forums which produced a lot of topics on this; I’ve read every one of them and even started my own.
MorganS Shannon Member Posts: However, when it’s on, most current is iirf4905 through this resistor, so heat becomes a concern.
Have you looked at purpose made Automotive High Side Switches? Perhaps a voltage divider which selects resistance to ground – likely through an “inverted” Q5b I’ve irt4905 tentatively added in D5s and R5s. Some drivers do have an always-on charge-pump though, you’d have to search for the right part.
This has consequences though; when the PMOSFET is on, all current through the resistor is shunted to ground – which produces more current than wanted via that route, so I thought maybe increasing the resistance when the Irff4905 is on, and decreasing it when it’s off would mitigate that.
Q5r has most everything spec’d at a V GS of 10V, so I thought if we can keep the maximum voltage at the gate to something resembling that, it should be easier to drive it back to ground when we want it back on.
One thing I can think that maybe should be included is a way to create a slight delay in Q5b turning off so Q5s can turn off Q5r a little “harder”? Gentlemen may prefer Blondes, but Real Men prefer Redheads!
IRF4905 MOSFET. Datasheet pdf. Equivalent
However, making them too small incurs inefficiencies – and likely the resistors will produce too much heat themselves. MorganS on Jan 31, The goal at the moment is to minimize R5r as much as Q5r will allow; its value was selected to drive about 2A into Q5r ‘s gate when Q5r is to be off, and when we want Q5r on, maximize the efficiency of the path to ground. TomGeorge on Jan 30, MarkT Brattain Member Posts: Lots of hints, allusions, partial answers, etc.
TomGeorge Design and Repair of industrial control systems. Commenting on variation “e” directly above: It is likely neither one will work as-is. Shutting it off is done via a pull-up resistor, and it seems that generally, the lower the resistance, the faster the PMOSFET will shut off.
IRF Datasheet(PDF) – International Rectifier
For this part, the requirements are: After a bit more stumbling around in the interwebs and learning tons more, I’ve ir4f905 up with a simpler solution he says hopefully. So, limit the lower voltage to something that will turn it on completely, and minimize the voltage swing necessary to shut it back off – maybe 1.
I’d be happy to hear of other or additional ways to minimize turn-off times while minimizing heat production from any components. You will have to draw a LOT of current through Q5b before you can get Q5s down to a voltage where you can switch it off.
lrf4905 What I know so far: So, D5s is there to limit voltage at the gate to 10V, and R5s is there to ensure it doesn’t release too much magic smoke the shown value should keep it to around 0. It can drive 6,pF in 40ns at 6A. We here have the problem that there is only an unclean 12V supply to work with, with spikes and dips, and standard high-side drivers for n-MOSFETs need clean stable 12V to work with.
While I have experienced some glimmerings of understanding, I don’t know how far off Irf495 am with ifr4905 the “5” or “3” circuits. Mark, Tom, thank you both for your comments. Most of such devices cannot PWM, they take ‘s of us to switch.
Krupski on Jan 30, When the main transistor is off, its gate must be about 12V, so the source of Q5s is about 12V and Vgs now is going to be negative – the transistor is driven on hard. Lots of interesting stuff there.
I’ve come up irr4905 a couple of other ways to speed up turning off Q5rbut they were tending to get more complex than I’d like.