Pic getting part power from Analog Port


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  1. #5
    Join Date
    Apr 2009
    Location
    Boise, Id
    Posts
    44


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    Talking

    Thanks for the information, I don't feel like I'm crazy any more, sounds like it's a problem some of you have experienced before. I attached a simple block diagram of the circuit I have. There is more circuit to build, but I need to get this part working and be able to handle low voltage and brown outs and recover without a glitch.

    To sum up what I understand so far: If power is removed from the Pic, but power remains on the I/O pins, the pic will become reverse biased. This puts the Pic into a Brown out stage. The default BOR setting for the pic was 2 volts. Since there was greater than 2 volts still on Vdd, the Brown Out Reset was not "reset". Changing the BOR setting to 4 volts in the include file seems to mostly fix this issue.

    To completely fix the problem, I need to add an additional circuit. The pic will control the circuit so when the Pic is powered down it will shut off the rest of the circuit, removing voltage from the Pics I/O pins. Also, there will not be any voltage on the I/O until the Pic Powered up and turns it on.

    Let me know if I have this correct. I'm using some Opto relays and Opto Isolators in other parts of my circuit. I could add those to the inputs and have the Pic control those to remove voltage from the I/O's. Might be over kill but I have them and would be easy to implement.

    Thanks again for the help
    Shane
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