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Dual port power OR-ing with power pass-thru

Other Parts Discussed in Thread: LM5069

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

  • Hi Tom,

    Do you have a block level diagram of the applciaiton?

    Also you might want to look at SNVA683. This app note discusses the extra protection circuitry you are inerested in.

  • Darwin,

    Here is the block diagram. It shows hot-swap controllers but probably be power OR-ing controllers. Anyway, I just need to be able to do UVLO and some kind of current control, either limitng or in-rush control. The A to B port shorting needs to go both ways so it may need to be two identical circuits since they usually only sense current one way. Does TI have a FET driver with some buit-in protection, possibly UVLO and current sense?

    Yes, I had seen the App note on the LM5069. Can Hot-swap chips like the LM5069 be OR-ed together? If so, it might work for the external source selectors, but does not work at the 3.0 volts needed for battery selector. The large disparity in input voltages is a challenge.

    Also, some kind of prioritization of source selection needs to take place. Battery is the default, but external ports will be used if available. Prioritization should be fairly automatic since they will always be a higher voltage than battery. If for some odd reason both external ports are available, Port A should be use. This should never happen because the other port is needed for communications, but someone may try it just to see if they can generate some smoke. :)

    Thanks,

    Tom

    MMotor Power Mux Block Diagram.pdf