Yeah, I get it. It works and stuck. Again, not criticicizing, just like to understand what's needed and what is just established and why. After all we are makingsome changes anyway probably, particularly the ldo voltage, so I can't just assume that won't have any effects. Now though I know, we aren't referencing of LDO (but I think not 1.1 either).
22 is a bit different from 19.1 (about 15% different OTC times). My point was more why not 20. I suppose people will need to order an LM3409 anyway, so adding a non-standard resistor value to the order doesn't really matter in the end. It's just a funny number. That's all, especially since almost all the rest are standard values.
At TA, yeah, 1.1 won't work without much higher resistance values than we're discussing. 2.55V (2.56 I think but whatever) is right as DB says (thanks for that feedback DB), and anyway, yeah, it's not vcc so that's the main thing because that's what I changed and wanted to make sure wouldn't impact anything. So 36K has worked and we'll use it.
Just for the record,
22k was introduced when driver boards were created where R1 was changed to a position before the diode D1. This allowed for more precise voltage measuring (while introducing OTC timing problems…).
22k instead of 19k1 compensated for the loss of the ~0.25V drop over D1, so existing firmware (mainly STAR back then) could be used on these newer drivers while maintaining the same LVP voltages.
Those were the days…
Yes, and it was a lot of try and error, some dead ends… and a lot of fun. Just like today, really.
It’s just that in these years BLF as a whole has developed an incredible base of hardware and firmware. And it still moves on.
To me some weird historical baggage is how the E48 and E96 series don't include the E24. Sure you can get 2% spacing with fewer resistors by starting over, but then you still ALSO need the E24 resistor values on hand anyway(if you want to be stocked up), so it's actually more in the end. I suppose it makes sure nobody accidentally uses 10% resistors when 1% is needed. In practice it doesn't really work out that way since 1% tolerance E12/24 values still get used at least as often as not, probably because people don't have to look them up. How often do you see a 1% 47.5 specced? Probably almost as often as a 48.7, but not nearly as often as a 47.0.
So about C1, it turns out it does want to be bigger, for the same reason many of the caps do, 4S, high voltage. I forgot that C1 is full voltage. In 0805 10uF ceramic or Ta, there are no x7R caps over 16V on digikey at least. Best I can do is a $0.57 cent 25V X7S ceramic. That should probably work for such a light load, on the other hand the cap is right next to the inductor pad. The 1206's are $0.20 in bulk, and basically one more is free if only making one driver anyway. So yeah, we can probably make due with an 0805, but ideally, it's specced as 1206.
I am not sure what all the rude clicking is about. The only one I have got was a post that everyone agreed was not rude. I just ignored it as someone having a bad day.
I will see what I can do when I rearrange things. I would not hold out high hopes though, it is really tight over there and DEL likes to see the traces as short as possible for all the MCU power leads.
Got the shopping cart almost done. This is going to be expensive. Heck it might be more fun designing it than buying it. ..yeah, looking like about $22 plus the board of course. Ouch.
Oh as for rude.. the button is right next to reply. I suspect that's the main cause. The op amp sounds good. It's the middle modes that are hard to get well with anything, and those are the modes I like.
In the grand scheme of things, spending $25 on a very advanced driver isn’t bad at all. Ok, so it’s not cheap, but what is these days and still holds value? So if we’re building a nice big light, it’s an essential qualifier for ultimate success. I don’t mind paying it, not every light would get a driver like this so it would remain a special build and would show the effort.
That’s one thing I’ve not understood fully… When the MCU is shut down, the OTC get’s discharged through the voltage divider? That means that the two separate pins are internally connected when the MCU is off?
I don’t understand it either but I have seen the effects first hand. Normal OTC calibration settings are in the high 100’s with the 19.1k but with the 22k resistor I had to bump it up to right at the limit of ~240 or so and it proved to be not as consistent in my testing. So I went back to 19.1k myself.
22k works fine, just more of a hassle to calibrate.
I’ve seen many report it so I don’t doubt it it all. I’d just like to understand why. Once I get home I’ll measure resistance over the pins on a MCU that isn’t connected to anything.
:person_facepalming: