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INA230: BUS pin input impedance

Hiroaki Yuyama TED
Expert 1720 points
Part Number: INA230

Dear, support Team.

It has a nominal value of 830 kΩ, but what is the maximum and minimum impedance over the full temperature range?
I’m calculating the error with the source impedance.

I saw the following link.
Is the tolerance percentage absolute value or +/- value?
https://e2e.ti.com/support/amplifiers/f/14/t/616595?tisearch=e2e-sitesearch&keymatch=INA230%20Bus%E3%80%80impedance

Best Regards,
Hiroaki Yuyama

  • 0
    TI__Mastermind 32395 points
    Hello Hiroaki,

    Thanks for your post and good question.

    The 830 kOhm resistor should not change much over temperature. In fact, the maximum temperature coefficient of the the VBUS input impedance can be determined by the Bus Voltage Gain Error spec in the datasheet (10 ppm/C typical and 50ppm/C maximum). This specification could be including gain error from the internal ADC, but since the bus voltage gain is dependent on change in the resistor, using the spec will provide a conservative max and min value of impedance over temperature.

    I will need to double-check, but I do not believe the absolute value of VBUS input impedance is trimmed. The absolute value of VBUS input impedance should vary +-20% over fabrication processes. This is a fairly standard variance for resistors. I will get back to you on Monday with an answer on absolute value variation.

    Sincerely,
    Peter Iliya
  • 0 in reply to Peter Iliya
    Expert 1720 points
    Hello, Lliya-san,
    Thank you for your Advice.

    I understood the correlation between gain error and input impedance.
    The calculation is done for the temperature sensor with source resistance over 100kohm.

    I am going to wait for an absolute value variation from you.

    Best Regards,
    Hiroaki Yuyama
  • 0 in reply to Hiroaki Yuyama TED
    TI__Mastermind 32395 points
    Hello Hiroaki-san,

    Based upon the process technology and design, the 830kOhm absolute input impedance can vary maximum +/-15%. This does not affect nor relate to the gain error of bus voltage measurement.

    The impedance will vary over temperature very little and this variability is less than the max gain error drift of 50ppm/degrees C.

    Hope this helps.
    Peter Iliya
  • 0 in reply to Peter Iliya
    Expert 1720 points
    Hello, Lliya-san,

    Thank you for your answer.
    My question has been cleared.

    Best Regards,
    Hiroaki Yuyama