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INA250 use case

Takao Yamamoto
Genius 4135 points
Other Parts Discussed in Thread: TINA-TI, INA250

Dear all,

I think to design like attachment file(TINA-TI file).

Are there something wrong or words of caution?

160509_DNWA_INA250A2_test.TSC

I use this for current detection of output of motor.

3.3V+/-5% is supplied to VS commonly.

Motor is activated DC24V (max 30V).

Best regards,

  • 0
    TI__Genius 15760 points
    Hi Takao-san,

    I will review the schematic and get back to you.
  • 0 in reply to Mayrim Verdejo
    Genius 4135 points

    Dear Mayrim,

    Thank you for your review.

    I am looking forward hearing from you.

    Best regards,

  • 0 in reply to Takao Yamamoto
    TI__Genius 15760 points

    Hi Takao-san,

    I have a few comments.

    1. You need to add a diode to your "simulation of your motor".

    2. The way you have configured the components around U3 (INA250 configured in low sensing configuration) forces the a 24V PWM signal into the INA250, that is not acceptable for our device. I have modified your schematic to fix that. Basically I moved the switch (T3), between the motor and INP.

    3. Please add bypass caps. Power-supply bypass capacitors are required for stability and must be placed as closely as possible to the supply and ground pins of the device. A typical value for this supply bypass capacitor is 0.1 μF.

    Hope this helps!

    160509_DNWA_INA250A2_test mod.TSC

  • 0 in reply to Mayrim Verdejo
    Genius 4135 points
    Dear Mayrim,

    Thank you for your answer, but I would like to know one thing.

    You said that 24V PWM signal into the INA250 is not acceptable.
    What is the reason?

    This device has 36V common mode voltage, so I think that this device can drive 24V.
    Is this wrong?

    Best regards,
  • 0 in reply to Takao Yamamoto
    TI__Genius 14825 points

    Takao-san,

    A fast-edge pulse, while not damaging to the device, will cause the input ESD cells to turn on very briefly.  A very small amount of heat is generated through the ESD cell.  Normally this is fine but providing sustained, high frequency pulses from a PWM will cause the part to heat up over time.  Filtering the signal at the inputs of the INA will slow the edges down and provide better operating conditions.

  • 0 in reply to Jason Bridgmon
    Genius 4135 points
    Jason-san,

    Thank you for your answer.
    I could understand that this device is not designed for high frequency case.
    Is this correct?
    If this is correct, can we read from data sheet about characteristics of high frequency tolerance?

    In addition,
    why does moving the switch(T3) from INN&GND to motor&INP improve high frequency tolerance?

    Best regards,
  • 0 in reply to Takao Yamamoto
    TI__Genius 14825 points
    Takao-san,
    Unfortunately our characterization does not include measuring edge rates and how they affect the part; there is nothing in the data sheet to say this.

    We suggested moving from an in-line current measurement position to a high-side or low-side configuration so that the part does not see the PWM fast edges like the inline position does.