LTC4416 Reverse Polarity Protection

I am using LTC4416EMS#PBF to switch between a 12V power source and a USB power source. The 12V supply takes priority over the USB supply as long as it's above 4V.

My issue is that my 12V supply needs reverse polarity protection. The LTC4416 datasheet mentions reverse battery protection but doesn't talk about that much. My assumption is that V1 and V2 will be fine under reverse polarity, but I'm not sure about H1 and E1-2.

Here is my schematic (capacitors are not shown):

So will this be fine under reverse polarity from the 12V supply (CAB) or should I add circuitry before LTC4416 to protect against RPP?

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  • +1
    •  Analog Employees 
    on Oct 12, 2021 6:15 PM

    Per page 2 of the LTC4416 datasheet, V1/V2 absolute maximum rating goes down to -14V, i.e., they can tolerate -12V without damage. Ex/Hx pin absolute maximum only goes down to -0.3V but their pin current is limited by the external divider resistors. It would be best to put in layout pads for an optional Schottky diode (i.e., GND to E1) to protect those pins in case there is a need for it later. Or, use a diode in series with the 48.7k resistor to block the negative voltage from the resistive divider and Ex/Hx pins.

Reply
  • +1
    •  Analog Employees 
    on Oct 12, 2021 6:15 PM

    Per page 2 of the LTC4416 datasheet, V1/V2 absolute maximum rating goes down to -14V, i.e., they can tolerate -12V without damage. Ex/Hx pin absolute maximum only goes down to -0.3V but their pin current is limited by the external divider resistors. It would be best to put in layout pads for an optional Schottky diode (i.e., GND to E1) to protect those pins in case there is a need for it later. Or, use a diode in series with the 48.7k resistor to block the negative voltage from the resistive divider and Ex/Hx pins.

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