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Finding current leaks

Adam Hoover
Intellectual 370 points

Anyone have any tips on tracking down current leaks?

 

In low power mode 3, my chip is supposed to pull 1 uA, but I'm reading 25 uA.

I've connected all unused pins according to manual specifications.

I've put all port pins in I/O mode, output direction, as specified.

Both these things helped me find ~200 uA of leaks, but I still have 24 uA extra.

I don't know what else to try - any suggestions appreciated.

 

 

  • 0
    TI__Guru 70602 points

    Hi Adam,

    some additional things to consider....

    1. Have you tried one of our LPM3 code examples as-is?
      http://focus.ti.com/mcu/docs/mcuflashtools.tsp?sectionId=95&tabId=1538&familyId=342
    2. Are you measuring the current directly into the device VCC or some other current which could include other parts of your system?
    3. Is any device pin driving into external circuitry (e.g., pull-up/down resistors, other ICs, etc).
    4. Is the current the same on different devices / boards? Sometimes a specific board may have an issue (contamination? some other manufacturing-related issue?) or a device may have gotten damaged during handling. Trying your chip in one of TI's bare-bone target socket modules will help isolating the issue.

    Regards,
    Andreas

  • 0
    Expert 2870 points

    Which device?  Are any internal devices left on, eg Vref?

    Hardy

  • 0 in reply to Hardy Griech
    Intellectual 370 points

    Thank you all for the tips.  Working from the demo low-power program helped.  To any TI rep, I'd recommend adding that, and the following, to the knowledge base / wiki.

    (1) The FET debugger uses additional current.  If you want a real reading, you must power the device externally, and disconnect the FET debugger.  Even if you pull the USB cable, thinking that it is not powered, it may still draw leakage current from the development board.  Disconnect it completely from the board.

    (2) Pull up/down resistors.  If, like me, you're not used to caring about current drain from them, realize that they can be meaningful when you're looking for uA leaks.

    (3) Partly faulty circuit, which was much easier to find once I figured out (1) and (2) above.

     

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