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I am trying to find a solution for ORing of 2 Lithium batteries, that also provides reverse polarity protection. Single cells are used, so the voltage will range from about 3V to 4.2V. Also, the two batteries need to share the load, since neither can supply sufficient current to power the load at peak demand.

A solution based on Schottky diodes, like in the image below, works correctly, but there's important power loss in the diodes, so I'd like to avoid that case. Ideal diodes seem like the way to go, but I haven't found an appropriate solution so far - the ones I've seen are not made for reverse polarity protection, and have low negative voltage maximum ratings (e.g., LM66100 with -6V).

Simple solution - Diodes

Simple PMOS-based solutions like in the image below work fine with one battery, but when you connect two in parallel they start conducting from one battery to the other. PMOS-based protection

The closest to a solution so far has been using two ideal diode controllers - MAX16171 - like in the image below. This seems to work correctly in simulations, but they are rated for input voltages from 4V upwards, and I need at least 3V. Ideal diode controller

I've tried to use the MAX16170 instead of the MAX16171, since it's minimum input voltage is 3V, but so far haven't been able to get correct results in simulations.

Has anyone solved a similar problem before?

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    \$\begingroup\$ Since a link to a document or website that has an answer is not considered an answer, here is a comment about a document that has answers: analog.com/media/en/news-marketing-collateral/… \$\endgroup\$
    – AnalogKid
    Commented Jul 25 at 13:34
  • \$\begingroup\$ The document has useful info, @AnalogKid. Thank you. I haven't seen a solution there that allows for ORing with load sharing, though (I've edited the post to include this requirement). I would very much like to simulate the circuit, and ICs from Analog Devices are ideal since I can find them in LTSpice. \$\endgroup\$
    – iEC
    Commented Jul 29 at 10:03

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Texas has LM74xxx family that should be exactly what you are looking for. LM74700 starts at 3.2 Vin, but there are other parts that start at 3V, like LM7481. AFAK, they all have reverse polarity protection and there are tons ob other features. The example how to use as OR-ing with reverse voltage protection, etc that is from attached datasheet: OR-ing enter image description here

Also data for LM7481: enter image description here

After a quick search it seems that out of this family LM7310 seems the best for you, as it starts at 2.7V. It also has integrated MOS, which is not always the best, but if it fits your application perfectly it can be a very elegant solution.

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    \$\begingroup\$ ursusd8 - Hi, Thanks for answering. However the referencing of the copied images is not sufficient. There is no link to the relevant source next to each copied image. || Having links elsewhere in the answer is not enough, as that doesn't make it clear (a) whether copied material elsewhere did come from those links; (b) even if the copied material did come from links elsewhere in answer, it isn't clear which material came from which link. || Therefore please can you add the link to the relevant source next to the copied material from that source. Thanks. \$\endgroup\$
    – SamGibson ♦
    Commented Jul 25 at 14:55
  • \$\begingroup\$ Thanks for your answer, @ursusd8. Indeed, the LM7310 seems like the right device. It can do ORing with load sharing as well, which is great. It would be reassuring if I could do a simulation with this IC, but have no idea how to go about it - it's not in LTSpice, and I haven't found the model elsewhere. \$\endgroup\$
    – iEC
    Commented Jul 29 at 10:08
  • \$\begingroup\$ I'm not sure about the LTspice. a lot of time simulation takes more time then quickly routing this part + caps etc and just producing with one of the fast online services. Does TinaTI maybe have a model if you want to simulate? \$\endgroup\$
    – ursusd8
    Commented Jul 31 at 12:31

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