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MSP-EXP430G2ET: Current consumption measurements Affidability

demetrio pitasi
Prodigy 20 points
Part Number: MSP-EXP430G2ET
Other Parts Discussed in Thread: ENERGYTRACE

Good Morning,
    we'd like to use MSP-EXP430G2ET to measure our device mean-current consumption using Energy Trace Technology.

The application loop under analysis is quite simple:

5 seconds of deep sleep + ~6ms of execution

During the 6ms of execution the product performs some measurements and a task that require one session of (~40x 4us load spike, one spike every ~60us).


Task Loop in time
                                                  _4us _                _4us _                         _4us _     spike
                             ___6ms___ /           \_60us__/           \__60us_.x20../           \    active
_______5s_____/                                                                                                \  deep-sleep


From an expected current consumption point of view (T rise/fall ~1us)

                                                  _60mA_                _60mA_                         _60mA_     spike
                             ___1mA___ /             \_1mA__/              \__1mA_.x20../              \    active
______100nA___/                                                                                                       \  deep-sleep

At the moment performed measurements don't match our expectations.

Some further details:
  all MSP-EXP430G2ET Jumpers  are disconnected.
  the device is directly supplied from the MSP-EXP430G2ET GND and 3V3  Pins
  a 47uF capacitor is installed in parallel to the device load
  We have verified and taken into account that the MSP-EXP430G2ET cannot measures down to 100nA

Taking into account all these pre-conditions the current consumption is still higher the what we'd expect.

So all these considerations lead to our questions:

Before proceeding with further investigations on our side, we would like to know
   1. how much we can relay on MSP-EXP430G2ET Energy trace capability to measure the current consumption in our specific application?
   2. is it capable to measure such short in time current excursions (1mA->60mA->100nA)?

Thank you very much for your support.
Kind Regards,
Demetrio Pitasi


  • 0
    TI__Mastermind 25570 points

    Hi Demetrio,

    The energytrace is typically used to get the average current consumption, though you can see some changes with the time graph it isn't really designed for the short bursts. It would be better to sample the specific bursts with lab equipment to get the bursts. But energytrace is accurate for average energy consumption of your system. Also this device only has EnergyTrace and not EnergyTrace++ so you won't be able to get different peripheral captures if you're trying to see a specific peripherals energy consumption.

    Below is the accuracy of EnergyTrace. 

    Regards,

    Luke

  • 0
    Prodigy 20 points

    Hi Luke,
         we are interested exactly in measuring the average current consumption in a deterministic loop.

    So you confirm that MSP-EXP430G2ET is the appropriate tool to measure this average, independently from how fast these bursts happen during the loop.

    We will thus proceed with further investigations on our side.

    Thank you very much for your support.
    Kind Regards,
    Demetrio Pitasi

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