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INA181: How could INA181 withstand 26Vcm > Vcc 5V?

Marsh Cai
Intellectual 2925 points
Part Number: INA181

Hi Teams,

Why INA181 can work normally with Vincm =25V, but Vcc=5V?

Is there some other special block working for common mode voltage attenuation?

Do you have some related block diagram to share to help to addressing this issue?

BRs,

Marsh

  • 0
    TI__Genius 13630 points

    Hi Marsh,

    This is a great question. This is also a very simplified block diagram.

    The input architecture actually level shifts the inputs from the high common mode voltage to the supply range, in your case 25V to the 5V domain. The level-shifted, differential input signal is then fed to the output stages (which is really just the rest of the internal device, specifically the differential amplifier and output stages).

    Does this make sense?

    Best Regards,

    Joe

  • 0 in reply to Joe Vanacore
    TI__Intellectual 2925 points

    Hi Joe,

    Glad to have your reply. You mean there's an analog level shift structure inside of the INA181? Which can realize common mode voltage attenuation without differential voltage distortion? 

    I used to think that level-shifter is only a digital logic level circuit, which can only deal with HIGH(1, 3.3V) & LOW(0, 0V).

    Do you have any pic or draft to share to address this? I am very interested in this circuit.

    BRs,

    Marsh

  • 0 in reply to Marsh Cai
    TI__Genius 13630 points

    Hi Marsh,

    I will try to look for some resources explaining the input structure. But yes, the INA181 input structure implements level shifting and biasing structures to allow for common mode voltages outside the supply.

    Thank you for your patience,

    Joe

  • 0 in reply to Joe Vanacore
    TI__Genius 13630 points

    Hi Marsh,

    I apologize for the delay here. I will provide an explanation or app note tomorrow. 

    Thank you,

    Joe

  • 0 in reply to Joe Vanacore
    TI__Intellectual 2925 points

    Hi Joe,

    No worries, looking forward your reply tomorrow.

    BRs,

    Marsh

  • 0 in reply to Marsh Cai
    TI__Genius 13630 points

    Hi Marsh,

    What I am explaining is touched on by the TI precision labs series on sensing.

    Transcript from video:

    We do not have an app note on this specifically but it can be something for the future. It is mentioned in the datasheets that the supply voltage does not impact the common mode range. The signal filtering section also touches on this in the datasheet. Section 8.1.3

     

    This explanation something I will take note of. Thank you for bringing this to my attention.

    Best Regards, 

    Joe