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Extreme power consumption

Zbynek Poskocil1
Prodigy 30 points
Other Parts Discussed in Thread: MSP430F5172

Hi to everyone!

I am solving a power consumption problem with my MSP430F5172. I am using it to control an accelerometer and a dual interface RFID memory. Everything is working as it should, but in normal mode the processor consumes approximately 68mA and in LPM3 56uA. I tried to change setting of all IO pins, but I did not find any which will lower the consumption. So I would like to ask, if anybody has any idea what might be a reason for such a huge power consumption. In the picture you can see a circuit diagram of my board.

Thank you in advance for any hints!

Zbynek

  • 0
    Guru 12050 points

    Are any used pins pulled down with internal resistors? as floating could result in rapidly changing pins = use power.

    Are any pin using pull-down while any of the external ic uses internal pull-up?

    How often are IRQs triggered in LMP3 mode?, to get down to 2uA you should only wake up 1/sec

    Are you measuring it while you have a programming board attached?, sometimes power flow from device
    and in to the programmers LED etc.

    R16/R17 is 0.95*Vcc enough to turn on the P-Transistor?  but transistors work on current so
    I'm not sure so that is why I only use p-mosfet
    with 2.2K pull-up (that is strong pull-up and only needed for superfast speed) are you sure you are tristate the
    mcu's SDA/SCL lines when not used or left as pull-ups?

  • 0
    Guru 46710 points

    Your problem can be improperly configured (as output, logical low) VEREF pin

    Zbynek Poskocil1 said:
    I tried to change setting of all IO pins

    What exactly did you do? Try __all__ pins as input __with__ pull-up enabled, check if it changes anything. This would exclude all "output short" and floating input conditions. If this solves problem - then you just have to find problem source and eliminate it

  • 0 in reply to Ilmars
    Prodigy 30 points

    Thank you for your suggestions guys. The thing is, that on the board where I measure the consumption is mounted only with the JTAG connector, MCU, accelerometer and their capacitors, then the EEPROM memory and resistor R10 and capacitor C5 for a reset circuitry. Other parts are not soldered so also most of the IO pins are not connected.

    I also tried to pul-donw/up all input pins without any big difference in the consumption. Anyway, I found out, that the VEREF pin, even if it is not connected thought R13, has supply voltage on its pin after reset and I don't have any idea from where the voltage gets to this pin.

    The use of external power supply with JTAG disconnected also doesn't make any difference....

  • 0
    Guru 227245 points

    VCORE MUST NOT be connected to VCC. It is the output of the internal core voltage regulator and all you may and must connect to it is a 470nF capacitor.

  • 0 in reply to Jens-Michael Gross
    Prodigy 30 points

    Thank you very much! The connection of the VCORE pin was the problem. After I delete the path between VCORE and VCC, the consumption is finally as it should be!

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