Don't have much time, but wanted to thank Alan and Eric for the capacitor analysis in Alan's thread, as well as ZapPat and rhitee05 on the commutation 'debate' on this one. Will await further enlightenment. I am more confident that 'enough' capacitance will fit on the board though.
Alan; as to board area, and I'm likely to get flamed for this, as I expect you and the other engineers who have mentioned that they are designing controllers on these threads are probably buffering all I/O.
I'm assuming a 28 pin processor, and other than the shunt buffers, I would be tempted to use nothing more than R/C filters, (which would be SMT), on various I/O. I've hooked PICs to the outside world through resistors to all sorts of things, including the 120v rms ac (for crude zero crossing detect). I would be tempted to use 3 resistors and a transistor to build the serial interface, but have to agree it SHOULD be isolated, and it wouldn't cost much board space. The hall sensors shouldn't require any special conditioning beyond an R/C filter should they? Of course the 5V regulator and associated filtering.
Jeremy, thanks for the link to LFP's new thread, they're always interesting. And of course thanks to LFP for the thread.
I I haven't found any 220uF, 100V Rubycon ZL in the US (haven't put much time into it), but I did find 20 for $10 plus $5 shipping, from Istanbul, on ebay (under about a dozen ebay names/countries). I think I would want the first batch sent to Luke for 'confirmation' of their esr.
What should they cost?
I finally found that 680uF 100V cap that I listed at the beginning of this thread. It has 27mOhm IMPEDANCE (@ 100khz), not ESR is why my subsequent searches failed.
(I'm going backwards through the thread, in case you haven't guessed.)
Alan, I would probably leave the diode on the board, in case someone thought they needed it. (Not every space will be populated, for every configuration.) Shane uses it in his controller is what caused me to think about it, and I think IR wanted one right across the gate in their early mosfet manuals (haven't seen one in 15 or 20 years).
The LVC on that IC is 12 an 13.5V. Assuming a similar part in Shane's controller, he may have felt the zener was needed because of his high gate drive voltage (I think 15v). I wouldn't think it would be necessary with a regulated supply, even as high as 16v.
I still think an economical version of this could be built for little more than $50 (75v/75a, or possibly even 100/100?)
But, what I want to see is one with copper water blocks, gold plating on the FETs, PCboard, and water blocks, (where current flows in and out of them), and air across the (4 layer) FET and driver boards. What does it take to melt that source lead's internal wire, or to melt the solder?!
Not what I meant to ask was it. :? How much current can we flow WITHOUT meltdown, if we really try and pull the heat off?
LFP mentioned a ferrite bead on the lead. At first (last week)I considered one on the gate lead between boards (for rf suppression), but decided it would fall into the same class as the zener. More questions ????
Bob