LED drivers and Accessories you want, but don’t exist

I inspected it with magnification glass and it looked like the IC had no connection to the inductor on the side where it is hidden behind C1
I used very little paste on the outer pins of the IC to do no shorts there

OK reflowed it with a bit paste and now it works
this driver does spot on 1.41A, probably a lot variation on this 3 stacked sense resitors

The IC itself has a feedback variation of +–5mV, the resistors have variation (1% or so), and the offset by the OpAmp adds some more.

Nice, now all drivers work?

I have found out that the driver gets pretty hot and the output current drops with higher temperature slowly

on my bench one driver quit working
it was the one with the capacitor

removing the capacitor and the driver shows a fast strobe
adding it again and it is dead

it looks like a bad ground issue, need to add maybe a bit more paste to the IC

A fast strobe? How fast? And it quit working? Was it still hot or cooled off already when the fast strobe occured?

Did it get hot in a flashlight, or was it on a bench uncooled?

Even though it might have 90% efficiency, 0.5W or so will be heat.

Schoki, since you mentioned that 3x3 MCU is the max you can fit I did some research…
Would Silicon Labs C8051F52x/3x series work?
They:

  • are available in 3x3 mm 10-pin DFN package
  • have 2-8 KB flash
  • have 256 B RAM
  • have a 8051 core, max 25 MHz
  • work in 1.7V-5.25V range
  • work in 40 125 °C
  • have a temp sensor and PWM
  • cost more than ATTiny ($2-$2.5 in small quantities)
  • can be programmed with open source tools on Linux and closed source freeware on Windows (dunno about Mac / BSD / …)
  • the programmer hardware costs $35

Though that said, the new attinies which we can’t program may be close enough to make the porting effort not worthwhile…

Thank you for looking for an alternative, i’ll look into it. But for now, I managed to squeeze an ATTiny25v on there, so bistro-hd would be possible.
The springpad is now smaller, but it should work (6.4mm diameter or so). It was possible because the ATTiny has one side of pins without any connection, so I removed these solder connections. On the other side, I just left the gnd pin.

One problem with other MCUs is that you have to change a lot in the code to make it run, so I hope it works like it is now.
I hope the 25v in a qfn package is a rev E at mouser. This is required to be able to run bistro-hd.

But since it’s a driver where a lot of current could flow, I maybe won’t even solder a spring on there. A piece of brass/copper could also work, and needs no bypass.

Hello.

Forgive me newbie question, but would it be possible to use something like TPS63024 for driving low Vf LEDs?…

If Vf is between 2.5V and 3.6V, yes.

Just ordered this, MP3431 board with (hopefully) bistro-HD:

It’s an 18mm board, but I’ll sand it down to 17mm to have copper right to the edge.

Ok, I finally found my way to thread instead of just the backroom PM discussions (that there have been a bunch of). Subscribed.

FWIW I've worked up a "Fet only" (ie single channel) configuration of bistro-HD (will be in next release, soon). Been meaning to anyway (actually a few such configurations, switch, indicator, OTMS, etc). It took a little compromising to match ramps to TA modegroups, mostly because without a 7135 you can't go below 11mA (1/255 * 2.8A) so modes get cutoff, but I've been thinking of ways to get around it.

16bit PWM, if the converter can actually handle such output or true, 2nd channel, enable pin PWM reduction, but Schoki says it's hard to fit the trace. 11mA ain't too bad though. It's not really moon, but it's low.

I thought I heard that this was going toward an attiny25 qfn, which I think is also on the scale of 3mm. Anyway, if you can make it still flashable (soic as shown), that's great.

For software though, if you need more space, the qfn becomes a drop-in replacement from the software side. Of course the qfn might make room for that extra trace.

It is attiny25 qfn, the tiny is on the underside. I removed the pads that aren’t connected internally of the attiny, the springpad is now a little bit bigger.

Is there a standard board or clamp or something you can buy to flash that or are you making up a flashing board too?

I use a USBasp and small wire that I solder on to flash it, for now.

You need 5 wires to flash. (power, ground, miso, mosi, sck) You're soldering them all by hand? Wow.

At some point it would probably be worth drawing a flashing board, that just connects via headers to the chip. It's got to be faster to just reflow it. Of course that requires work too.

Well, shoot only $85:

https://www.amazon.com/QFN-16BT-0-65-01-Programming-Adapter-Socket-Enplas/dp/B00KG7T8PU

So this is a buck driver?

If this works it would be nice to try to get one with Narsil

Also thought about a driver with a slave board to get more useful space

To solder and unsolder 5 wires for programming takes a minute, nothing wrong for a small to medium number of drivers

I don’t need the reset pin to flash?

It’s a 1S boost board.

oh, yeah, forgot reset. Yes you need that too. 6 pins.