With the Noctigon linear driver the LED can take a second or so to lit up on the lowest level (not sure why), with jump start apparently it starts at a higher level then go back to the actual level.
Dynamic PWM : likely to prevent noise during thermal throttling, since the PWM runs at 4kHz (10bits) in the Noctigon driver the bulk 0805 cap can sing. So here resolution is decreased to 8 bit for the FET and frequency increased to 16kHz so that it’s not audible.
No, to change the timing to get higher resolution in the lower levels. Like 1/10, 1/9, 1/8, 1/7, 1/6, 2/10, 2/9, 2/8, …
Ah yes, I assumed that was the implementation starryalley’s dynamic resolution but no.
I reflowed my first 1616 MCU last night on my tweaked gchart 20 mm driver boards. It's just an old FET+1 but what a PIA soldering that VQFN-20 part. I must have made like 8-10 attempts at it, but hoping the next will go easier. I made my own 22-23 mm version that can be sanded down a couple mm's to fit various lights.
One of the 23 mm's sanded down will be going in a cheap 18650 small zoomie with an e-switch. By cheap I mean like paying $7 shipped.
I think what I'll do is use very little solder paste for the middle pad, and don't reflow the pins. For the pins I'll hand solder with just laying a thin stripe of solder paste across each side of 5 pins, then working it with the small tip iron. Might need the solder wick as well.
For the one I did last night I first tried paste all around and ended up with big balls of solder on each side, crossing all 5 pins. Eventually what worked was hot air removal of the MCU, solder wicked the pads clean, then hot air reflowed the MCU back on. I think the MCU had enough solder on the pins to bond well and still stay clean. All this time the driver was on a 100C hot plate.
Personnaly I’m using a stencil I made a while ago, just for the 1616.
Another way is to tin the pads and then reflow.
Ohhh, maybe the tinning method will work for me. Think gchart said the stencil didn't work well for him.
Hmm, maybe it’s because I’m using printing grade paste but I haven’t had any issues with stencils.
It’s been a while since I’ve used a stencil. I haven’t used one since getting new higher-grade paste. I need to try again.
So is that type 4 or 5, like described here: https://fctsolder.com/solder-paste-type-3-vs-type-4-vs-type-5/
I had to google it... 
Looks like 4, or better yet 5 is better for small parts/pads.
Is higher grade the type 4 or 5? Any links, let me know. Thanks guys!!
Out of curiosity, what thickness of stencil are you using? I think that could play a big factor as well.
And I’d have to look Tom, but I think I got the type 5 stuff. That and my old stuff was crusty and had been re-fluxed several times.
Mine is T4, it’s just that the printing grade one is less fluid, I think it’s so that it releases well when lifting the stencil, though I actually never tried stencils with the dispense grade (syringe) I have too.
0.1mm steel.
Oh I think puting flux in paste is very bad, I tried to put flux in some of the print grade to make it more fluid, one month after it didn’t work at all.
I use Chipquik no fridge (quite practical) Chip Quik - Solder Paste No Fridge (15)
Pot is print and syringe dispense.
But it’s not cheap
Ok, if I were to order this, I think I would want for solder paste:
https://www.chipquik.com/store/product_info.php?products_id=470011
and for flux:
https://www.chipquik.com/store/product_info.php?products_id=310017
I think the tack flux is the typical type? Not too thin, watery?
And definitely the leaded paste for me.
That paste would be amazing if refrigeration is not required. Any downsides?
Oh, by "print" you mean using stencils?
Update: Just found it on Amazon US, cheap but Halogen free: https://www.amazon.com/Smooth-Leaded-Solder-Paste-Syringe/dp/B08KRR7PV4/ref=sr_1_6?dchild=1&keywords=solder+paste+t4+syringe&qid=1629334633&s=hi&sr=1-6
Regular, leaded, more $$$:
Ooops! My bad! Those on Amazon are not the Thermally Stable ones (TS...)
For the flux I use SMD291, it’s not too thin I think, the one you linked is a RMA type flux and isn’t described as ”no clean”, that said it’s still RO*L*0 I.e. low activity so maybe it’s fine ?
I haven’t noticed any issue with the no fridge paste, but mine only 6 month old.
Print grade (sold in pots, see in the datasheet) is specifically for stencil, it doesn’t work well for applying the paste manually, it doesn’t stick well and kind of stays on the tip of the syringe. I’ll test stencil with the dispense grade (sold in syringes) next time.
This is what I've been buying, current syringe from Jan 2021: https://www.amazon.com/gp/product/B017RSZFQQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I keep it in the refrig, but occasionally forget and leave it out for a day. It's really not sticking too well, and stays on the syringe as you described for the print grade. Not sure if it's from the age, leaving it out, or what. Think it's worse now though then it used to be, not sure. It's probably dried out some.
Yea, that RMA291 looks good - thanks! Now just wondering if I should commit to the $$$... Wish I had the ability to design and layout my own drivers 
. You two are doing great jobs on the drivers, btw!! Very jealous
Well without talking about the circuit design, it didn’t take me too long to learn how to use an EDA software (I use Kicad, I think eagle and easy EDA are also popular ?) just by following tutorials. Making drivers that fit in whatever host is quite rewarding.
For the circuits, FET+7135 are very simple and there must be some shematics on the forum, the linear driver above if it works properly I’ll share the schematic (the boards shipped a few days ago).
For the paste not sticking well, pre applying a thin layer of tacky flux helps (not too much otherwise the paste spreads out)
Using a small dispense tip is also better, less area to stick to, I use red plastic ones… hmm 24G I think it is (they are color coded). For precise dispensing, using a small syringe is incomparably better than the one the paste comes in, I use 1mL ones.
Edit : thanks for the compliments 
Yea, I know the ATtiny85 FET+1's all too well, and have OSHPark drivers of them to accommodate just about anything, many dating back to 2017 from DEL and Texas_Ace mostly. CC linear and optionally a full FET with power efficiency and no visible PWM is preferred now.
Ideally, the most desired support would be having true regulated constant output (lumens) up til a certain power level, depending on the light's design, no visible PWM. Not sure if this requires buck/boost - think so? But certainly for a single cell driving a 6V or 12V LED, then boost is all that's needed, I assume. Same for just buck needed if 2S-4S cells, 3V LED. But certainly for single cell 3V lights, buck/boost with a wide open FET channel would be the best setup?
Gchart's runtime graphs on the SP10 Pro are dang impressive! (https://budgetlightforum.com/t/-/56521)
I have mixed opinions about buck boost due to their lower efficiency and low input current limit. The ones from TI are limited to a peak input current of 4 or 4.5A IIRC, which means that at 3V in they can boost to maybe 2.5A, the most powerful buck boost converter with integrated switches that I know of is the newly realeased LT3120 from Analog with 9.5A average input limit which is much higher and with four 25mΩ switches, better as well. But still if you look at the efficiency graphs page 7 it still dips significantly at higher current in boost mode.
At 2.6Vin 3.3Vout, it dips to 70~75% at ~2.9A out and quite steeply, the graph page one shows 3V to 5V at ~2.9A with 80% efficiency so that’s better, might be able to do 4A at 3Vin 3.3Vout.
It’s quite expensive so I hesitated buying some when there was a few available early July, now it wont be available until mid 2022. It has a relatively larger footprint than TI buck boost converters.
I think for single LED it can make sense, for multiple LEDs I’m less convinced since with the lower Vf a linear driver or a buck in dropout are still able to push some current.
About the FET+ buck-boost topology, it has the issue (with Lume 1 drivers) to not have PWM dimming on the FET channel
One reason is the noise generated due to the 4kHz frequency, but TK new PWM code should solve that.
The second reason is that the FET and BB channel can’t be ON at the same time contrary to linear/7135+FET.
For the latter you ramp up the CC channel to its max say 3A, then the FET starts to add brightness on top of that.
With the former you ramp up the BB channel to 3A, then when the FET turns ON the BB must be OFF, but since FET is unregulated we don’t know what duty cycle gives us 3A and I it is Vin dependant so that we can’t ramp up smoothly from there.
I thought Zebra was known for compact buck/boost, but maybe amp limited, but thought they were one of the best efficient drivers. I don't really know the details though. I'm sure you are right.
Where I work they just bought $75K worth of parts from brokers, like twice the regular price, but will get us about one year in production. It's scary, desperate times.
The SC64c actually uses a 3A buck converter. The SC/H600 MKII did use a buck-boost, I don’t know about the other 3V models.
Yeah, yesterday a bought some boost regulator, a few minutes after that they were all gone from Mouser and Digikey, even the ones in order for the end of the year, that was close 
. I was actually wondering if with the current situation there might be scalpers.
Ahh, so if the SC64c uses only a buck, it would drop output/amps when the battery drains below a certain level, least on the high modes?