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Linux/AM5728: APM sense resistance vs temperature

solid repellent
Intellectual 850 points
Part Number: AM5728

Tool/software: Linux

Hello,

I am using TI AM572x EVM board. I am measuring the power consumption across the APM sense resistor R34 (OHMITE,  LVK12R010DER) to get the power consumption of the MPU subsystem. Now, I want to run some experiments by keeping the ambient temperature constant and measure power consumption. I am using a temperature control chamber for this purpose. I plan to go from room temperature to 65 degrees ambient and measure the corresponding power consumption. I am worried about the effect of APM sense resistor's resistance changing with the temperature and the amount of effect it would have on my power measurement. Could you please throw some light on this?

https://www.ohmite.com/assets/docs/res_lvk.pdf

Is it that the resistance will increase by +/- 10% ? This is not very clear from the datasheet.

Thank you for your time.

  • 0
    TI__Guru**** 393215 points
    Hi,

    The component you are referring (OHMITE, LVK12R010DER) is third-party, not manufactured by TI. We cannot comment or give advice on third-party documents. Please contact the component manufacturer for support.
  • 0 in reply to Biser Gatchev-XID
    Intellectual 850 points
    Hello,

    Without going into the specifics of the component, could you please throw some light on the effect of temperature on the resistance of the sense resistors (in general)? If there are any ways, I can mitigate them? or measure power consumption effectively?

    Thank you.
  • 0
    TI__Genius 13567 points

    Hi Solid,

    The datasheet says LVK12 series has a 50ppm/C temperature coefficient and a rated ambient temperature of 70 degrees C. Based on that information and the formula from this guide. You can calculate the maximum change in resistance. Considering the rated temperature of 70C and your test temperature of 65C, you can say the change in resistance due to temperature is almost zero.

    There is a temperature sensor (U4) that is placed about half an inch from the processor. The sense resistors are also about half an inch from the processor. You can use that to double check the board temperature and calculate from there. 

    Regards,
    Ahmad