Ok, I spent the morning re-working the driver for what is hopefully the final version.
I was able to increase C1 to a 1206, removed the jumper and generally compacted everything for as much edge clearance as possible. Still not a ton though, only about 3mm at the closest points but that is just enough to clear most of the SRK’s I have laying around.
If this looks good to go then I will put together a completed package along with a shopping cart link and people can give it a try at their own risk.
Nice work, a good looking board. I'm a bit surprised you left the Ruv's in. It won't hurt though. I guess you're worried we won't ever figure out R1? It defeats a good bit of the space saving though. I will try to dig through source and code and attiny manual code and if I can get to the bottom of the R1 thing.
Might reach 15A for some seconds. 0.6V dropout should be achievable at that current level in theory at least, for a perfect battery of course. The driver is capable of opening up to 100% duty cycle, basically direct drive, but with a bit more resistance from parts. It can take 16.8V input.
So I'll work on the last changes to the shopping cart soon, but what about about heat sinking? There is no exposed copper on the edge. I don't have an SRK. If the copper there was exposed could it be made to contact the case? Maybe with some thermal grease at least?
I left then in because taking them out didn’t free up any edge space and I am always a fan of cramming every possible option into something if there are negatives.
Look it over carefully, I will give it a day or 3 to let us all figure out any possible issues and then I will put together an official release.
Yeah, I was debating this myself. Obiously we don’t want it grounded to the case and shorting out but as long as the tailcap side is not shorted to the case then it should be fine. It is easy enough to expose the copper on the edge like normal.
Can't the outer edge of the tailcap be ground? connected directly on tail-cap side to ground pad, and by vias to outer ring on component side? Ground touching the case should be fine, right?
Would set the 2.56V reference for attiny 25 and attiny 8, but really should add a define, and might be different in attiny13, and needs changing in a couple of places and might interfere with temperature readings (but I don't think so, it's got separate code), etc... So doable, but not quite just flipping a switch.
Anyway that line and the details behind it confirms that the way things are setup now is for 1.1v, so I agree, that's what we should use for now at least.
The only question then is what total resistance to aim for for acceptable drain current. is 95k enough or should we double R2 and bring it all up to the 200k range? I don't like 900k.
Well sure it is, exactly inverse proportional. Ok, I think 11k and 220k was good when I checked. No time to run the numbers now, but something very close to that is good.
We missed one. According to your LDO TA series docs, C2 should be 10uF when using an LDO, which makes sense. This one at least is low voltage, so really doesn't need to be physically larger. This is why we waited a few days. Updates coming soon.
Well rats, so yeah, C2 is only available in 6.3V X5R in a 10uF 0603. Price isn't bad at 0.13 per one. Your usual comment TA is that an 0805 will fit there. Is that still true in this one? It looks possible to slide C1 north about a mm, if it goes back to not jumping the trace (trace turns between c1 and c2). Is there room to squeeze an 0805 on as it is?
On the other hand, X5R is probably ok. There's an X7t also. Not sure which is better, probably makes little difference. In the long run, it looks like C1's are headed toward 0805 with this new OTC trick. sigh. There is a way, to even get the footprint, moving the trace between them, and then sliding C1 left a bunch. I know you don't want to make that a long trace. If we can just have enough clearance to fit an 0805 on the 0603 pad, that's good enough too though.
