What is a good current sense reading

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  • DadBuk
    Member
    • Sep 2021
    • 11
    • Australia

    #1

    What is a good current sense reading

    Hi, have searched high and low for some info on what a good current sense reading is as it applies to MacBooks. On a MacBook there are many isense signals and it seems logical that the higher the voltage of that signal then the more current is flowing through that rail. What I have not been able to determine from the schematics or from searching the forums is the voltage range of a current that is in spec versus one that is out of spec and therefore causes the MacBook to take some action. I see in the schematics there are values for the max current on a rail but nothing that looks to be the voltage range for the current. I tried reading through the data sheet of an opamp that is generating one of these signals but could not work it out from there.

    Is there some simple way to calculate this or are there tables of these values that I am yet to stumble over.

    Thanks
  • piernov
    Super Moderator
    • Jan 2016
    • 4435
    • France

    #2
    Re: What is a good current sense reading

    Use Ohm's law to find voltage at the input of the current sense amplifier (across current sensing resistor), then apply current sense amplifier gain to find the voltage at the output of the current sense amplifier.
    Current sense amplifier gain may be written in schematics or in datasheet of IC for dedicated current sense amplifier, otherwise if discrete opamp it can be computed from the resistor values.
    ASD will report anything reading outside of an acceptable range.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

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