Your email never appeared, which means that there's trouble on my end. A more reliable email address was just emailed to your yahoo addy. usenet on my end is getting upgraded to provide functionality such as UTF-8. My upgrade will include a proper usenet email address. Sorry about the mixup.
Thank you,
-- Don Kuenz, KB7RPU
Got it this time. Bless you. You're a good man. Your spreadsheet makes it much easier for me to perform a secondary sort on the parameters that Tim mentions elsewhere in this thread. Neither DigiKey's website nor Mouser's website help /me/ much with winnowing out the best device (although others here find those websites satisfactory).
Thank you,
-- Don Kuenz, KB7RPU
Have fun.
It's often useful to create a F.O.M. column for a tradeoff parameter, such as capacitance or maybe charge, times Rds(on), and search on that, rather than on just one parameter.
--
Thanks,
- Win
I wish DK, et al. had such a feature. Alas, even just getting consistent ON data is challenging -- DK just reads the datasheets, so whether the mfg rates a part for Rds(on) or Qg(tot) at 5 or 10V (Vgs(on)) is a crap shoot. They record this at least, but you have to pick through the values yourself.
If we demanded that mfgs report their FOM at such-and-such condition, it would get there, eventually. But, yeah...
You can at least use the relative values of the parameters to make a selection. Calculate the maximum possible Rds(on) you can tolerate in your application, then select equal to or lesser than that value. Around the max, snoop around for Vgs(on) = 5 vs 10V parameters, and add/remove selections as needed. Example: for a 5V drive application, you might remove items that are 10V and more than half the required Rds(on) -- because Rds(on) is ~ very roughly ~ half at 10V what it is at 5V. Conversely, for a
10V application, you might add items that are 5V but up to twice the required Rds(on).Then select the top (least) half of Qg(tot) max, or more or less depending on how much of that parameter your application can tolerate. (Remember gate drive power is Qg(tot) * Fsw * Vgs(on). It can add up quickly, when Qg and Fsw are large!)
Finally, sort by price or quantity, or further thin down the selection based on package, power rating, or others.
Oh, and all of this after first selecting packaging (if you need, or don't, tape&reel or what have you), stocking, and voltage rating (and maybe current as well, but you'll more-or-less get that with the Rds(on) selection).
This pretty quickly narrows down a full 45,593 catalog to maybe a few dozen items, and you can flip through datasheets from there. All in all, a complete selection might take 10 minutes. Yes it's a PITA, but in this age of the paradox of choice, you have no recourse but to work through it.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
I use FAEs to do the bulk of the legwork. I tell each what's important and have them come back with a list of the cheapest parts they have that match my criteria. Each will come back with five or six that look interesting and they know what's being used elsewhere in the company that I may be able to get volume leverage on. Sure cuts down the pile of datasheets I have to go through.
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