I need some help finding the best solution for a fairly complicated power management requirement..
This product (module) will have three sources for power, internal battery (3.0-4.7V) or external (12-18V) from either of two ports, all positive voltage.. The internal battery will be used by default unless either of the external sources is available. If power is coming from one of the external sources (ports), it must also be made available the other port. Identical modules can be daisy chained together, passing power along to the next, up to three total in the chain. Power consumption for each module (motor controller) is 3W running, 1W idle, and 12W in a stall which can last indefinitely.
A high degree of idiot-proofing is desirable, so reverse voltage, current limit, short-circuit protection is a must, with UV/OV LO for preventing over-discharge of batteries, surge protection.
I've been looking at power OR-ing controllers to bring the sources together, then a hot-swap chip for protection and inruch control, perhaps using a Power Good signal from the hot-swap chip detecting external power and using that to enable a pair of back-to-back N-ch FETs as a switch to give a bi-directional connection between the two ports for passing power. Just how to drive that I don't know because it also needs some protection. It needs something like a hot-swap chip but have it go bidirectional with current limiting. Not sure how, but I suppose it needs to protect against external power sources being plugged in BOTH ports and one back powering the other. It's getting a little crazy. And, of course, the simpler the better since board space is scarce.
Anyway, if can you offer some suggestions and/or critique of these ideas, I would appreciate it.
Thanks,
Tom