Ok, ok, MOM :)…
Earlier, you were thinking 3.15 amps… is that still attainable you think?
And yes, I can measure the winding wire diameter then.
I wouldn’t sweat ~3A, whether it’s 2.8A or 3.2A or whatever. Not everyone agrees with my decisions though and I certainly don’t know everything. There is a lot of unknown stuff happening in that driver.
Those tiny parts just don’t look like 4A would be their friend. For that matter they don’t really look like >1A would be their friend though, so who knows.
So we’re talking about the 2 pins on either side of the end of the chip away from the dot, right?
When I try to measure pins 3 and 4 voltages, what do you want that relative to? Is the ground ring ok?
Yes, 3 & 4 are the pins farthest away from the dimple.
Unfortunately I’m not 100% sure what’s going on there. We’d better start by measuring everything against the outer ground ring, but we may end up measuring against that big crescent shaped trace that everything* seems to hook up to. I don’t really understand the purpose of the separation between the “true” GND ring and the other one unless it has to do with implementing the Zener diode.
*This is what I mean by everything:
303 resistor
104 resistor
cap
W8 diode
S4 diode (err, I guess it’s not hooked up to the crescent)
cap / white thing
R200
AOEC #2
Hi,
Toroid OD (NOT incl wire, I think): 8.05 mm
Wire diameter: 0.30 - 0.40 mm (I took several measurements, I think some parts of the wire was near where it was soldered)
Voltages to (emitter side) ground ring with driver in medium mode:
Pin 3: 4.18V
Pin 4: 0.115V
EDIT: My resistors shipped from Digikey (25 0.1 and 25 0.2 ohms)
We really need to see all 6 voltages for best results. (I’ll most likely still be guessing though!)
Aack! I interpreted what you said as just needing pins 3 and 4:
NP, I’ll try to do all pins, but probably not tonight…
Sorry, poor choice of words on my part. I look forward to your results when you get a chance.
Thanks for those dimensions, ohaya.
Resistors arrived from Digikey today:
You have to love Digikey (seriously)…. does that packaging look like a bit of overkill or what - I included the pen in the pic for scale :)!!?
I haven’t been able to get all the voltages on the 6-pin chip yet (couldn’t get to the one side w/o possibility of shorting something), but here are voltages to the (emitter side) ground ring with driver in medium mode that I have so far:
Pin 3: 4.18V
Pin 4: 0.115V
Pin 5: 3.12V
Pin 6: 0V
FYI, the resistors arrived, so I put 2 x 0.1 ohm resistors (R100) in parallel, and the current to the emitter goes to 4 amps at about 5V and above. I have one of those laser thermometers, and checked various points on the driver, and temperature seemed about 80F.
I tried a short test where I cranked the Vbat/Vin up, but I thought that I saw some smoke, so I shut it down.
The driver still worked after that, and I visually inspected with a 30x magnifying glass and I didn’t see any obvious (to me at least) signs of damage. Also, there wasn’t any “burnt smell” that I noticed, so maybe I was just imagining it.
We know the SS34 Diode is only rated to 3A max continuous, so that is one part I would be watching for the magic smoke to get out. Maybe look for some bigger diodes in the parts drawer.
I kind of suspected the SS34, since that’s the part that got kind of lifted off of the board when I pulled the R200 earlier, but it (the SS34) still looks ok (no blistering/bulging, no burnt odor), but it’s possibly on the underside, that I can’t see.
Would these work, both electrically and size-wise:
??
And if they do work, does that mean I’d be able to run 5 amps?
EDIT: According to this, the SS34 is DO-214A package also, correct?
EDIT 2: What about this one from Digikey (the qty 1 one, not the qty 3000 one)?
I was just thinking of something (it happens once in awhile), and have a stupid question: How is it that the MCU on the 16mm driver doesn’t just get fried when I, say, put 9V input?
I’m not sure MCU is the proper term for that thing. Regardless of the terminology, I think the answer is that a zener diode is used to power it. Google has simple diagrams for a zener and resistor together, that is the arrangement I’m referring to.
Ahh. Ok, so it’s similar to what comfy does with the 7135-based drivers, i.e., use a zener to drop the Vbat/Vin to a voltage that the MCU/controller can work at.
Any idea if that diode I linked at Digikey could be swapped into the driver and let the driver work at 4amps?
FYI, I’ve gone ahead and ordered a couple of the SK510L-TP diodes from Digikey and will try to swap them onto one of the drivers and see if it’ll run at 4 amps (or maybe more, I also order some 0.05 ohm resistors :laughing:.
EDIT: Pretty soon, I’ll have enough parts to build these drivers from scratch like you all do on the Oshpark projects :)!!
We’ll see how it goes. I suspect that the best case scenario is that efficiency is quite low with the tiny FET. :~
This whole thing should be interesting, huh? I have a few places where I can/would really like to use a tiny 4A, 2 x Li-Ion driver awaiting.
Yeah, I know exactly what you mean. I think a fair number of folks here really want a small, powerful buck driver. I’m definitely on the list. After we’ve got that hammered out I suppose the only thing to do is focus on a small, powerful boost driver 