Tool/software:
I have a project that includes TWO power limited sources A and B, each capable of about 15 watts of power and each of variable voltage (one is not always higher than the other).
A single BQ25790 is really great at using ONE source of energy within a specified power limit to supply the load, and if it can't supply enough power then it will start to draw power from the battery.
For a DUAL BQ25790 design, I would tie the SYSTEM power and the BATTERY together for both chips. I then want the first chip to draw up to 15 watts from source A, if that isn't enough to supply the system load, then I want the second chip to draw energy from source B. If A+B do not have enough power for the load then I want the system to draw from the battery.
The only way I can think of doing this is by manipulating the BATTP voltage sense connection on the second chip to strip about 100mV off what it thinks the battery voltage is. In this way, Chip A will try to regulate VSYS at 200mV higher than the battery, while Chip B will think the battery is lower, and therefore would try to regulate VSYS at 100mV higher than the battery.
I think this will force A to power first, then B then Battery.
What I don't like about this solution is that the datasheet is not very definite about just how much higher VSYS is regulated above the battery voltage. Therefore, trying to play around inside that voltage zone seems risky, plus it depends on both chips having pretty tight voltage reading tolerance.
Can you suggest any other way to get two BQ25790 (or another TI chip) to play nice together? Making use of the power available to them, but in a well defined way of A then B then Battery...
NOTE: I know this part has a built in power source selector, but I want A plus B... not A or B.
I can't just use ideal diodes because I can't guarantee if A>B or A<B or A=B.
Thanks!