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LM66100EVM: RPP in OR-ing application

Abdelhakim ERRAOUI
Prodigy 80 points
Part Number: LM66100EVM
Other Parts Discussed in Thread: LM66100, TPS2121

Hello Experts,

I am testing the LM66100EVM board with an OR-ing application where I use two batteries for Vin1 and Vin2.

I have noticed that when I reverse one of the batteries I measure a current of around 20mA coming from the non inverted battery to the input. So I am wondering what is the source of this current flow ? Maybe a reverse current flowing?

to resolve this issue, I added two PFETs in series with the input of each LM66100 (please see the image below)

What do you think about this configuration ?

PS: the board jumpers are configured this way :

JP2,JP7,JP1,JP4, JP6 : Removed

JP3, JP6 : connected to Vinx

Thank you in advance for your reply,

  • 0
    TI__Genius 10652 points

    Abdelhakim,

    The PMOS you have connected serve no purpose, they cannot block reverse current as they are always turned ON. You would be better served by a schottky diode but there will be VF losses. 

    During a reverse polarity of the battery, it can damage CE pin maybe and the device PFET may still be on, the gate could be 0V to -Vbat which can 

    In the ORING configuration, LM66100 can't effectively block all reverse current/have reverse polarity protection as the RPP config can't be used along with ORING. 

    CE pin is also not designed to handle -ve voltages below ~-0.6V, so in ORING configuration, it should not support reverse polarity of the supply. 

    You would need to add protection diodes, extra ideal diode ICs with Reverse polarity protection configuration, or simply ensure that the batteries can not physically become reversed. 

    I recommend you to take a look at an eFuse TPS25942 which has B2B FET topology rather than single PCH fet and very robust protection mechanism against reverse polarity. 

    Also recommend to look at TPS2121 which has B2B FET topology rather than single PCH fet and can protect against reverse polarity conditions

    Best

    DImitri

  • 0 in reply to dimitri james
    Prodigy 80 points

    Dear Dimitri,

    Yes using a diode has the drawback of the Vf losses. And the issue with PMUX ICs is the high quiescent current that is too much for my application battery life requirements (I need to be in the range of 10 - 20 µA)

    I totally agree with you about the fact that the PFETs won't block reverse current but Let's say that I am not worrying that much about reverse current as the output will always be inferior (enough) than the input (correct me please if I am wrong).

    I tested the configuration with the two PFETs with both or one battery inverted (for long period) and I have protection against RP and there is very small current flowing (~300nA) to the inputs and no heating. Also the PFET turns off as soon as the battery that is connected to is inserted backward. I'm not sure if I misunderstand something in this solution, maybe its not really reliable but it works.

    Best regards,

  • 0 in reply to Abdelhakim ERRAOUI
    TI__Genius 10652 points

    Abdelhakim

    If your testing shows that the PFETs are effective, then please feel free to use those. My idea was that they potentially wouldn't work but if that doesn't seem to be the case based on what youre seeing no issues to use them.

    Best

    Dimitri