After doing some testing I’ve pulled the current sense amplifier from the control package. Too difficult to stabilize the control loop with the extra delay of that circuit in the chain, in addition to considerations like added cost and board space. I reckon it’s enough to divide down the filtered PWM signal. Done some hardware testing and it’s working so far with a little 2A driver, stable down to about 0.5% output power.
Next comes software. The PWM code is working fine, so what remains is ADC sampling of the off-time capacitor for mode switching, battery level monitoring, and eventually interfacing to a temp sensor for thermal throttling. I don’t have the temp sensor to test but I can simulate its signals. My hardware test board is a home-etch (sharpie resist in HCL/peroxide bath) but it works pretty well so I should be able to test everything and get functional code with a day or so of focus. I know for you guys this sounds a lot like reinventing the wheel but I don’t like using other people’s work, especially if I intend to sell it.
likevvii, I assume you’re asking how thick the 8A boost driver will be. I don’t know, and that particular design is a fairly low priority for me. I probably won’t even start prototyping until I have functional boards of the penlight, 3A buck and 5A boost. I’ll probably want a FET tailswitch too. I’ve got parts in to test with, but currently no PCBs and everything’s such fine pitch that it’s near prohibitively difficult to home-etch boards to mount ’em up. I need to work on my toner transfer abilities.