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INA4180-Q1: exceeding input pin voltage

Aivaras Sakauskas
Intellectual 1420 points
Part Number: INA4180-Q1

Hi,

I have a question about the differential voltage on this part. The datasheet says it can exceed 28 volts as long as the current is limited to 5mA.  We want to sense the voltage across a FET.  When the FET is off, the inputs will see battery voltage.  In some cases the inputs may see a load dump voltage of 35v.  Is that an issue if the current is kept below 5mA? can you please provide more context of the 5mA value?

Thanks

  • 0
    TI__Intellectual 760 points

    Hello Aivaras,

    Thank you for the question and using the E2E forum.

    If current injected into part does not exceed 5 mA, the part will not be damaged. The issue is that in introducing resistors to limit current to the 5mA threshold the gain of device will be altered as ratio of resistor network is changed. This is not easily accounted for as internal resistors are trimmed to a ratio and not specific values. This means that accounting for any adjustment in effective resistor network has additional inherent error. (see equation 4 and table 9-2 on data sheet). Due to this effect, this implementation is only viable in applications that can handle significant degradation of accuracy.

  • 0 in reply to Joseph Scherphorn
    TI__Intellectual 1420 points

    Hi Joseph, 

    Thank you for the background. How can they know if they are not exceeding the current? Is there a specific range for internal resistors?

    Also, the datasheet mentions sustained operation between 26-28V can cause permanent damage. What is sustained operation?

    In any case, the bottom line is that they want to make sure the device can survive a load dump up to 35V or will the device get damaged? In that case they need to account for protection.

    Thanks

    Aivy

  • 0 in reply to Aivaras Sakauskas
    TI__Intellectual 760 points

    Once device input grows beyond 26V ESD diodes turn on and so internal resistors are not relevant. The resistance on these diodes is going to be very low once ON threshold is reached. References to conditions beyond 26V in data sheet are speaking to device survivability only. Device is not intended for operation beyond 26 V and is only spec'd to survive these conditions below 5mA. This should not be an intended operation condition. Current can still be limited as discussed above with external resistors on front end however this will introduce error (see equation 4)