[WIP] *15mm* DD+single-7135 driver - single sided Dual-PWM compatible using 3.3x3.3mm FET

No, the reflowing itself is not what holds me back, I think i can get it done quite nicely, it is the yet again new (mostly magic to me) components that I need to find in small quantities with affordable shipping to the EU, and my unability to flash my own firmware (I am not much into electronics and in computers, even do not have a proper Windows one).

I think there's many folks out there that would love to use all those great drivers, but despite of not being afraid of some DIY soldering, lack one or two skills to make a functional driver starting with a bare Oshpark board.

Oh hell yes. This is going directly into my titanium D25A. And hopefully also into the brass AA lights from CNQG, if it’ll fit. I think I have hosts for about half a dozen of them.

The D25A will probably get special firmware, since it has a sensor for fully-tightened vs slightly loose. Not sure what to do with that yet though.

Thanks djozz, i have seen your measurements all over this place :slight_smile: so i have to be honest, when you say it is possible enough with the hollow pill it gets me curious, because you are right about the great dislike about this here, and me as new at this have almost adopted this as a truth, without any real personal experience backing it up.

So i wonder have you used any thing in that size with a fet driver and didn’t feel it lost a lot of output fast by bad heatsinking? i
thought a solid pill/shelf where almost a requirement to not have it sink like a stone in lumens output.

A DTP MCPCB is a requirement for that, and so is a decent path from there to wherever all this heat is going. Beyond that, more contact the better of course… ideally the whole chain has very few thermal interfaces and the interfaces are all good.

Interesting this means i have disqualified some possible nice host wrongly then, i will keep this in mind for future builds, thanks wight and djozz for setting me straight.

Way to step up, wight. When I get a chance I need to update the Oshpark projects thread with all this new stuff. Won’t be anytime soon though.

I think it might be a good idea to mention that one reason for bypassing the diode to the voltage ladder is to allow Zener mods that still have lvp with just a change of R1.

I figured you’d like this one; I know your mind’s been on 15mm drivers for a bit now.

Thanks RBD. It’ll be nice to have this stuff in the OSH Park projects thread, but I suspect that it’s also time for me to put a thread together just to organize my drivers, outside of my signature. RE: the bypassed diode thing - good point. That description started off a little lacking and I’ve copied it between my driver threads without improving it.

BTW, I think I’ve asked you before, but where do you like to order Khatod optics? Cutter? Or maybe a source in the US?

Apparently I still haven’t figured out how to find specific parts on mouser. can you link for the correct FET?

I haven’t picked one out (and I will not be doing so immediately).

Please use these instructions to help find one. See what you come up with by focusing on these things, mostly in this order:

  • I’d stick to 20-30v rated stuff
  • high current rating
  • a fairly low gate threshold voltage since it will be powered by no more than whatever the MCU gets as input. Take a look at the graphs in the datasheet for PSMN3R0-30YLD which show Rds(on) vs either Vgs and Rds(on) vs Id. Remember that our Vgs will be lower than battery voltage… it’s battery voltage minus the voltage drop in the diode and in the MCU. I usually eyeball the performance around Vgs = 3.3v.
  • gate charge – don’t let it be too high. Look at the other selections we’ve been discussing, but I think you should be fine with <50nC or <100nC or something.

Cutter Electronics has them but both price and shipping are high.
Both are taller than Carclo quad optics and don’t fit the same peg radius as Carclo 25mm quad even though the led locations are the same. On some mcpcb’s all that’s needed is to open the peg holes to the edge of the board.

Thanks, that’s what I was afraid of (the cost in dollars, not the peg layout).

How about:

PSMN4R2-30MLD
or
SiS414DN

I’d call SiS414DN the clear winner for this application except for the fact that it’s in a flat-no-leads package. I expect that it will be very difficult to solder for most people. (Actually reflow only for most people I think…). It’s also “Package Limited” to 20A, but I don’t think that’s very relevant here. PSMN4R2-30MLD has more exposed leads and should be a bit easier to hand solder.

EDIT: Clearly I made a mistake. PSMN4R2-30MLD is not that great.
EDIT 2: Clearly I can’t read a datasheet. SiS414DN isn’t that great. I made an error with units (ohms vs milliohms).

I have not evaluated the following FETs beyond Rds(on). Listed in order of Rds(on) performance at our voltage levels:
PSMN2R4-30MLD
PSMN2R8-25MLC
PSMN3R0-30MLC
PSMN3R9-25MLC

Possibly functional, but not characterized well by the datasheet (for our purposes):
PSMN1R5-30YL
PSMN1R5-25YL

Not considered due to high Vgs threshold:
PSMN4R0-40YS
PSMN3R3-40YS
PSMN2R6-40YS

Ok I just added some PSMN2R4-30MLD to my order. hopefully they end up working for our purposes. Just to confirm, other than the FET and the 22k resistor, everything else is stock from a 105c, correct?

You also probably want a 1uF offtime cap such as C2012X7R1E105K125AB

I have some 80-C0805C105K4R in my cart, that will work right?

That’s fine, no problem.

Oh man..... Is life getting good or what ?

I was wondering when/if anyone would incorporate the smaller LFPAK size but resisted suggesting it because of the tight pin spacing(I barely get by on attiny’s and 7135’s). Curious to see how much better it might be than the 2502 or it’s successor(you listening Dale?).

He's asleep in your back yard. Yell a little louder and he may wake up.

I agree, the pin spacing is very tight. Fortunately only one pin actually needs to be separated from it’s neighbors. Still, if a person is a beginner at reflow soldering I’d say that this is not the place to start their journey. The same thing applies doubly to hand soldering.

PSMN2R4-30MLD vs AO3400? Single LED performance is what matters for this driver I think, and that should restrict us to looking at higher Vgs numbers vs triples & etc. At 3v Vgs it seems like we’d have around a >20milliohm difference in favor of the PSMN2R4-30MLD, which translates to maybe a 0.08v difference in voltage dropped over the FET. To me that looks like approximately half an amp. As you know, all this napkin math doesn’t get us very far. We’ll have to wait for them to be built and tested. (of course it should beat the 2502 by a wider margin)