Lucky, eh? I guess v032: OSH Park ~
- Corrected R1/R2 silkscreen.
In this case practical experience is driving my decisions. A datasheet’s recommendation isn’t golden. In this case we’ve got a driver which will be clamped into a metal retaining area. We’ve also got a 7135 with a thick slab of metal on the bottom which is doing much more than a 1oz trace ever will. It’s simply not going to help. Whoever modified the v013 layout attempted to follow the datasheet for no good reason in this case - it’s as simple as that. They also didn’t even get close to what the datasheet recommends FWIW…
Additional info:
- 7135s behave very well when overheated. Even with the driver air-wired inside a big light I would not expect issues.
- Current firmwares, AFAIK, generally run the 7135 at a very low duty cycle. It doesn’t really matter for the reasons I stated above, but I thought it was worthwhile to point out nonetheless.
Again, practical experience is what’s guiding me here. Take a look at the Nanjg-105 for another example where this is not a problem.
There are several issues here. #1 is that this driver is not intended for your application. Certainly another layout can be done, but this one is simply not ideal. Square peg, round hole.
There is no sane place on top to solder a 1.5mm solid wire and not rip off traces. IMO a good match would be plated-through-holes sized for the 1.5mm solid wire.
I’m not certain what your overall goal for that project is, but this is a hotrod driver. The v030+ purposefully skips current-carrying BAT+ vias and depends on a spring bypass. Anything which defeats the spring bypass is outside the scope of the v030+ layout currently under consideration.
IMO DD/FET drivers may be poor design choices for the sort of light you are thinking of (potting etc generally indicates something which is not a hotrod). We wouldn’t use a hot-rod engine in a police interceptor car.
As far as not trusting the bypass wire… feel free not to trust it. It’s necessary if springs are used. Folks here are using it. The big 3mm via is specifically intended to make it easier for less-skilled folks to do a bypass which holds up better and longer… (while also allowing Dale to use 18awg } )
Once we hammer the details out I’m sure that a layout for non-bypass applications will happen at some point. If nothing else we’d simply replace that center via with a pad and put many smaller vias on the board as I’ve done with other layouts.
I use and recommend this free product: gerbv - A Free/Open Source Gerber Viewer It works quite well and handles the drill files properly.
I suppose that there are also leakage specs that should be considered?
I suspect that 100nF will work. We’ll see. The bounce is a good point.
One thing to consider is that while the MCU pin may be rated for XX mA, the FET gate could easily get much much more current than this during the turn on. I suppose that it’s kind of a moot point since we’ve got C1 though…. hmm.
Two points here:
- We really only need full saturation while we are at 100% duty cycle. Anywhere else who cares? 100% duty cycle is where we get no boost at all. If we were having a problem getting the gate voltage high enough during 100% duty cycle I suppose we could drop it to 254/255 but then again… if this was a problem we’d have noticed hot MOSFETs by now.
- FWIW the SiR800DP kind of makes this a moot point too. That thing is ridiculous.
Good point, Mike C would be a good person to ask. I selected PSMN3R0-30YLD myself back when I released the A17DD-SO8, but better FETs have been found for our applications - See DB Custom’s post #381 on the topic. FWIW I believe that Rufusbduck picked out the PSMN0R930YLD and comfychair picked out the SiR800DP. My testing earlier in this thread was done with the PSMN3R0-30YLD because that’s what I had it’s not bad.
I’ll take a closer look at the WP article, thanks. I see that it touches on the important design considerations.
We can look into a design for that, but I think it would be worthwhile to just airwire it for now. That might give us a better idea of feasibility & etc. Once a more concrete range is known for the C1 value we can attempt a fresh layout with an SMD larger than 0805.