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TM4C123GH6PM: TM4C123 ADC Power consumption

Ahmed Kamel
Intellectual 935 points
Part Number: TM4C123GH6PM


Hello, I am using TM4C123 ADC to measure the internal temperature and want to calculate it's current consumption, i can't find a reference in the micro-controller data sheet about the ADC current consumption.

Thank you

  • 0
    TI__Guru 72500 points

    It is in table 24-41, on page 1399 of the datasheet.

  • 0
    Guru 117855 points

    My impression is that Mr. Crosby's chart presents the "entire" MCU's current consumption - both w/all peripherals on (top) and then w/all peripherals off. (bottom)

    A method to determine your objective (the ADC's current consumption) may involve the disabling of ALL MCU peripherals - then making a current consumption measurement - and only then enabling the ADC - and making another measurement. Under those conditions - first all OFF followed by ONLY the ADC peripheral ON - the difference in current draw (we suspect an increase) should reveal the ADC's current consumption...

    As to that chart - the difference between "Nominal @ 105°C" and "Max @ 105°C" appears suspect.    (one would expect the values, "nominal" @ 105°C to (somewhat) approach the "max" value @ 105°C.   They do NOT!)

  • 0 in reply to cb1_mobile
    Intellectual 935 points
    This is a right method, but suppose that you don't have the required instruments to measure the current consumed by the embedded device, and want to estimate the current that will be consumed by making analysis to your system and active peripherals.
  • 0 in reply to Ahmed Kamel
    Guru 117855 points

    Ahmed Kamel said:
    ... without the required instruments to measure the current consumed by the embedded device

    You may then "borrow" the methods used by many Eval Boards - impose (install) a small value, non-inductive resistor - between your board's regulated 3V3 and your MCU's VDD (& VDDA) power pins.   (hopefully/usually that regulated 3V3 is routed via a single pcb trace which then "branches" to serve multiple MCU power pins.   (you do NOT want to add multiple resistors - use just one - and insure that its location is very strategic.)

    Ohm's law will suggest a good starting value - that's left for you.    

    Realize too that the chart provided here does NOT include the MCU's system clock.  (while in Run Mode)   For this vendor's MCUs to properly enable the ADC a minimum frequency of 16MHz is (usually) required.   As you know - higher frequencies increase the current consumption...

  • 0 in reply to cb1_mobile
    Guru 117855 points

    Note that the voltage drop across this added resistor must be "slight" (~0.25V max) so that the MCU receives adequate VDD/VDDA level.

    You must perform your two voltage measurements (each across this added resistor) "after" this resistor (placed in series) w/the MCU's regulated 3V3 has been installed.

    Vendor's chart does not deal with the ADC's consumption (actually avoids that detail) and that consumption is likely to vary depending upon the number of ADC channels enabled & the conversion frequency. As always - devil resides in such details...