Another little driver that won't be much use to most of you guys

I see your point with the 20pin MMU. If I start making a fortune by selling pre-flashed MCUs, you be the first to know…
In the meantime
With the 20pin version GND sits differently (which is the least concern). It’s larger. And lot’s of Do-Not-Connects on both sides.
You use Eagle? You might want a custom part stripped of DNC pads so you can use wires under the MCU.

Is there going to be a problem with the MCU because of the back/bottom GND plate not being soldered down?

I have no idea what is needed either, only that it apparently works lol.

Since I do not see this driver being used in anything but a 1S setup using an internal voltage reference should work well.

Only if the MCU produces more heat than the package can dispose of without the soldered back. I can’t find anything substantial in the datasheet. But I truly assume that, as our Attiny13A are in sleep mode almost all the time, that it will work fine without the added heatbridge.

You’re probably right. Additionally, this driver only has a single 7135 regulator, and will be running off a very small Lithium cell. So heat from all sources will be quite low.

Edit: So, any chance you’d sell me some pre-flashed 10 pin MMU’s?

Yeah, I think there is even more heat coming from the LED to the driver to the MCU than is generated in the MCU itself.

As I wrote, if I start making a fortune by selling pre-flashed MCUs, you be the first to know…
No, honestly, I do not sell, I only have a flimsy breakout board and I’m not capable of testing post-flash. Did I already mention I sit in europe?

But RMM might be able to do it, if he already sells the 20pin, why not the 10pin? Might just ask him.

Oops! I missed that post of yours before. :person_facepalming:

I hadn’t thought about making a new library part. That would work well enough for what I need. If I do that, as well as removing the LVP parts and moving everything around a bit, I could possible get the driver under 11mm diameter. Then it should work for most 10mm cell size lights (10180, 10250, and 10440/AAA) as long as they have length enough in the driver cavity.

Don’t give up on the 20pin MMU yet, being able to get these preflashed from RMM is still a major asset.

Here another proof of concept, which might be very much along the lines RBD suggested:

Make C1 an 0603, use 0.254 instead of 0.3048 wires, squeeze everything tight together and you might even hit the 11mm mark… But the 20pin is huge compared to the 10pin…

Thanks HQ! :partying_face:

My pleasure :beer:

Time zone trailer, I’m missing the fun. Yes, I meant that since you can’t flash after there no need for clip clearance. Blank areas, traces, and vias all take up space so smaller blank areas, shorter traces, and sharing vias with no top side ground ring all will help. Post 19 is along the lines I was thinking only better, I hadn’t thought out how to arrange them. Even just eliminating the mmu pads on the left side will allow the R1/R2 trace to pass underneath so you can squeeze the 7135 down a bit more. When Mattaus did the first tiny10 it took some time but in the end it made sense looking at it.

It’s usually we CET-guys that are missing the action :slight_smile:

Nice work DavidEF. Sounds like it will make a nice driver.

You could save some space by nixing the reverse polarity protection. Not sure what impact that would have on internal reference LVP.

Another thought, with left side mmu pads eliminated, swap the 7135 with everything but OTC and route pwm under mmu. Maybe rotate the mmu so the gnd side flat is aligned to the board edge instead of it’s corner and put a gnd via under the mmu.

The inner yellow circle has a 5.5mm radius (->11mm).
Getting closer.

Gaining space below the MCU doesn’t help, no component fits. So I swapped D1 to the right again.
Still the notorius OSH Park Edge­­™ has to be considered. :frowning:
But it looks promising.

@DavidEF, if you want the .brd with the custom parts, PM me an email (preferably an anonymous one).

Now my TimeZoneGap will commence.
Goodnight.

L+/L- could be much smaller(1mm) if they were vias solder able from the bottom. 10xxx cells are all small contact on the positive end so a .4mm (?) via should work for L- if between B+ pad and outer ground ring. B+ input via becomes L+ eliminating that pad altogether.

Wow! You guys are great help! RBD, thanks for all the great space-crunching ideas. I meant to work on this board again this afternoon, but I forgot. I’ll have to try to remember tomorrow afternoon. HQ, thanks for all the work you’ve done on those board designs. Don’t worry about the OSH Park Edge­­™ being a problem. These boards can be sanded down pretty easily. I’ve been adding extra diameter to my boards just to accommodate it. If we can get the real diameter to be as small as possible, then the OSH Park Edge­­™ doesn’t really hurt anything except making the boards cost a bit more.

Update January 4, 2017: Ignore this post. See post 40 from DEL. This board isn’t going to work.

I made a new, even uglier version of the driver! I deleted R1 and R2. LVP will have to be implemented using the internal voltage reference. By doing that, and also using a chopped down MMU part, I was able to add another 7135 and still squeeze everything into 11mm! To clarify, the overall size of the board is still 13.28mm including the OSH Park Edge­­™, but all the components are fit within a 5.5mm radius from center, so it can be sanded down as far as 11mm diameter. Just sanding down the OSH Park Edge­­™ only still gives a 12.5mm diameter, which is what I’ll be using if I get to do my mod.

Did I say it was ugly? :confounded:

That weird shaped exposed copper at the top left is the LED and the other one at the right, hanging dangerously close to the ground pad of the 7135, is the LED+ solder pad. Sorry RBD, I didn’t use your idea to make those into vias. I also didn’t label very well. Only D1, C1 and OTC are even labeled at all. But at least I got my name on the back! LOL! I may go back later and clean up the look of this board a little and add labeling for components. Maybe. I’m tired now.- :weary:

What size is the C1 pads? The smallest 10uf I know of is 0805, which can be installed on an 0603 pad but nothing smaller.

It’s a 0603 pad, but it will indeed be a 0805 cap. I guess for consistency’s sake, I could either make the OTC pads also 0603 or change the C1 pads back to 0805. I just didn’t think about that last night. I guess I was more tired than I realized. :weary: