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LM74700-Q1: Reverse Polarity Protection Charger+Battery+LOAD

Asael7
Intellectual 270 points
Part Number: LM74700-Q1

Hi. 

I am working in a system where I need a reverse polarity protection board between a charger and a battery (10s4p, 42V max).

First i thought of using a low side protection as shown in next image:

But with that circuit, reverse polarity protection would work if in the external system only was a load not battery, because battery would activate the protection circuit even if the charger is not connected.

For that problem I think to use a simple solution as a diode, knowing voltage drop in the diode, as in the image.

But I have problem yet, diode protects against reverse polarity for the external charger, but battery also could be connected in reverse, so, the diode is not a good option.

Other option that I think is use a smart diode as LM74700 or LM74610 with a MOSFET but if I don't wrong, would be the same effect as the diode but with a low drop voltage. 

I was checking other options but I don't have a solution yet, a solution that could protect against charger reverse polarity or battery reverse polarity without the battery activating the protections when the charger is not present. Is there a way to use smart diodes and have the solution that I need or could you help me guiding me on what the solution might be or recommending an application note

  • 0
    TI__Genius 16305 points

    Hello Asael,

    Thanks for posting the question on LM74700, we will review the requirement and get back to you within today.

    Regards,
    Kari.

  • 0 in reply to Karikalan Selvaraj
    TI__Genius 16305 points

    Hi

    Case 1: Reverse polarity protection when external charger is connected in reverse polarity

    In this case an ideal diode controller such as LM74700-Q1 is recommended to protect the battery from discharging.

    LM74700-Q Controls an N-channel MOSFET and it turns off the N-channel MOSFET when reverse current (reverse current flows when charger is connected in reverse)

    Case 2: Reverse polarity protection when battery is connected in reverse polarity.

    In this case, the LM74700-Q1 + N-channel MOSFET will allow current through the MOSFET. If the charger has output short circuit protection, then the short circuit protection will trigger and turn off the charger output.

    If the output short circuit protection is not present in charger, another high side switch (N-Channel MOSFET) or low side switch is required to turn during output reverse polarity (battery side).

    Could you please review our initial feedback and let us know if this protection topology works to meet your requirement.

    Or are we missing anything.

    Then we can suggest on the implementation.

    Can you share the battery voltage, charger output and current requirements here?

    Also if you would like to share the end application of this protection, we can suggested more suitable solution.

    Regards,

    Kari.