I have the same question, will we be able to measure phase currents by using multiple high-side amps.
Honestly I do not know.
I have spent few hours in research and it seems to be very very unusual approach, maybe even too unusual. I was not really able to find anything about it. Here are some very nice pdf’s explaining different approaches:
This article is also nice:
The guys says:
High-side dc-link sensing is typically used only for fault detection. It has the advantage of having a stable common-mode voltage and enables motor fault detection. However, depending on the motor, the common-mode voltage could be very high, limiting the choice of devices able to be used in this implementation. In addition, the driver current, which is actually what’s being measured, doesn’t necessarily equal motor phase current.
I suppose for DC motor it really does not matter which one of the current sense techniques you use because there is always only one current. And high-side is nice because you can sense the short-circuits. But for BLDC’s it seems to be very uncommon technique. You can see that in all of those links above you will not find multiple high-side current sense amps.
But in regards to your question, I would still suggest you to separate them. And then, if that is the only way, you can sum the adc readings in the code.
I have made a board that uses the btn8982 as well, and it will come I hope tomorrow so I’ll look into it a bit more in depth. It would be awesome if we could do current control using these drivers, it would make these drivers absolute winners!
If not, that would mean that we need to add additional current sense resistors and amps to the board, and that all becomes complicated.