17mm & 20/26/27mm single-sided DD/FET driver release: A17DD-SO8 / A20DD-SO8 / etc

is the PSMN2R4-30YLDX still the best candidate? or is there a better option now?

Also, when I’m ordering diodes for D1, there are a lot of specifications, but which ones am I actually looking for?

I don’t remember any discussion on the PSMN2R4-30YLDX, and i can’t find anything on this when i search BLF.

But the PSMN0R9-30YLD or the SIR800DP-T1-GE3 i believe is considered to be the possible higher performing than the usual PSMN3R0-30YLD from the OP.

EDIT
Do you mean the smaller LFPAK33 PSMN2R4-30MLD when you say PSMN2R4-30YLDX?

PSMN2R4-30YLDX

Yeah i found it on google also when i searched on it, but you said “still the best candidate” implying that this was common knowledge that it was, thats how i read it anyway.

When i compare the fig.8 “Drain-source on-state resistance” in the data sheet i think the PSMN0R9-30YLD looks much better.

I assumed it was highly regarded at one point because it’s what mtn sells.

Ok thats interesting, then i am also curious why :slight_smile:

I hope some of usual MOSFET gurus here can chime in, or maybe RMM himself.

In a Zener modded board the gate voltage will never fall below 4V so it should be fine. It’s possible that one with better fig.8 numbers might be better for single cell DD but not enough builds with other options to know if it’s worth it to spend $5 a piece for them.

  • I think that figure 10 is the most telling when comparing those two FETs. By my reading of figure 10 PSMN3R0-30YLD is clearly superior to PSMN2R4-30YLD. (When scrutinizing the datasheet this difference is first noticeable in figure 7, but it’s not clear why… figure 10 shows why.) Both MOSFETs are suitable for use with this driver. Since PSMN3R0-30YLD is less expensive and appears to be the better of the two I’ll continue to recommend it.
  • I think that DBCstm has decided to go with SiR800DP for future builds, although I know he’s got a few other FETs on hand at the moment such as the very expensive Toshiba units. I don’t think I’ve seen a side-by-side, but it’s always seemed pretty clear that the SiR800DP would firmly beat the PSMN3R0-30YLD. [compare “On-Resistance vs. Drain Current and Gate Voltage” in the SiR800DP datasheet with Fig10 in the NXP datasheets] SiR800DP also costs over double vs PSMN3R0-30YLD. I doubt that most folks will gain a lot by spending the extra.

What about the PSMN0R9-30YLD?
Just a slightly better/more expensive 3R0?

I’m currently building drivers on the 0R9, will get some 3R0 later for comparison.

PSMN0R9-30YLD certainly appears superior to PSMN3R0-30YLD… but at that price why not buy SiR800DP? It should be both cheaper and better.

If you look back through this thread I’m sure you’ll see discussion of PSMN0R9-30YLD. Compare the datasheet graphs/figures RBD and I mentioned.

We use Figure 8 primarily to see where the ‘knee’ in gate voltage happens. We can’t really glean much information beyond that from Fig 8, don’t read too much into it.

Use Figure 8 as an “at a glance” to see whether you should even consider a MOSFET. Once you’ve confirmed that the knee is in the appropriate place focus on the other graphs to get a better idea of performance between good FETs.

Well, I feel my FET question is sufficiently resolved. What about the diodes? The ones I have work fine, but when I reorder I would prefer to get ones with “the line” to show polarity instead of “41” written on top.

What am I looking for in the spec lists to determine if it’s what I want?

  • It must be able to withstand the full battery voltage in reverse.
  • Low Vf at around 5mA.

The 2R4 and 3R0 are really pretty dang close. I wouldn't pay extra for the 2R4, but it was available in large quantities when I placed my last order, the 3R0 was not. I've used the 1R0, 2R4, 3R0, and 4R0. Between the 2R4, 3R0, and 4R0 it is hard for me to differentiate between them. The 1R0 may be measurably better with fresh cells, but it is hard to tell. It seems like how hard I'm pushing the battery against the spring seems to make more difference at the top end than the FET used. I haven't tried to measure yet down in the 3.6V-4V range, just wide open with fresh cells.

The one that really stands out as a great performer is the SIR800DP. I think that I would take that over the 0R9 or 1R0 for single cell use because entire curve is shifted to lower voltage, which is what you need when your batteries are getting lower. All of them work awesome at 4V+.

I'm wondering if you would see a greater resistance decrease from simply removing the polarity protection diode than you will from going from a $0.65 to $2 FET. Has anyone measured the gate voltage under load with and without the diode in place?

Thanks for chiming in RMM. I think you hit the nail on the head with this bit:

I haven’t measured the gate voltage. Or if I did I was working on something else and didn’t keep track.

I would not think that you would net more than 0.2v at the gate by removing the polarity protection diode… which should net you an improvement of less than 1mOhm under load with the PSMN3R0-30YLD… not a big gain, but that might put it on par with the PSMN0R9-30YLD. I do not think that removing the diode would put PSMN3R0-30YLD on par with SiR800DP, which is currently cheaper than PSMN0R9-30YLD anyway.

Removing the diode might get PSMN0R9-30YLD on par with SiR800DP on fresh cells, but why would anyone bother? SiR800DP still seems to win in general.

The question is whether it's worth $0.50 extra per driver to go from the 3R0 class to the SIR800DP. With the 6V+ emitters it definitely isn't, but I'm not sure yet for single cell use.

Thanks guys :slight_smile: i don’t know why i so enjoy these kind of discussions, i have really tried to get a grips on how it all functions but when they keep using different scales to describe the same feature & i try to recalculate it to compare the graphs in my mind i always fail :frowning: no matter how hard i try.

Maybe thats why, it is almost a little mysterious to me :smiley: someday maybe someday.

The biggest thing i got from this was that i had almost totally missed that the SIR800DP was seemingly now suddenly (to me ;)) the strongest performer.

And the removal of polarity protection diode “mod” if one could call it that, so SIR800DP+no diode :bigsmile: = max possible performance :bigsmile: + some extra pressure on the spring if possible = even more :smiley:

Just to double check so i understands things right, because i just realized that i totally missed to buy any diodes anyway. the diodes is the “D1 – SOD-323 & SOD-723, assorted” from the OP (i mistakenly thought that was for the with Zener functionality only) can any one give me a good pointer on what to buy.

I got wight’s
It must be able to withstand the full battery voltage in reverse.
Low Vf at around 5mA.

And i saw pilotdog68’s point about easy markings, so i don’t have to measure every time i want to make sure.

I can find SOD-323 at 5v but i haven’t found one with 5mA yet just way above, that makes me think i am not even on the right kind of diode yet.

So what are you who are already building these using?

Is this the correct type?
I have tried to find one but i can’t find one that is in the range of the whole 2,5v-4,3v for single battery use & with a Low Vf at around 5mA
And if try to include a marking also i get even worse hits………

No, that is the wrong type. I did not think to mention it when pilotdog68, but it must be a Schottky diode.

There are carts on page 2 of this thread. Those include an appropriate diode. While there are certainly better options on the market, the ones in those carts are the ones I’ve tested.

me too, it’s a real joy to follow these discussions.

So my next order will be SIR800DP…

cajampa:
http://www.mouser.at/ProductDetail/ON-Semiconductor/NSVR0320MW2T1G/?qs=sGAEpiMZZMtQ8nqTKtFS%2FIMZb%2FvX%2FZJHlCuzGQtxqeU%3D
This looks pretty usable for D1

I’m sure this is answered somewhere but I’m unable to find it atm.

Is the input of the voltage divider connected to Vin or to the output of D1?
Output of D1 would mean voltage monitoring with the Zener mod is not usable because the max input of the divider is the Zener voltage?

EDIT: rtfm - everything is in the 1st post