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INA199: 20mA detection Question

CHO SR
Genius 3225 points
Part Number: INA199

Hi,

The customer configures the same as the data sheet circuit below.

Supply : 9V ~ 18V

Rshunt : 0.05ohm

The circuit function is to detect a current of 20mA flowing through the Supply - Rshunt - Load.

Rshunt to detect 20mA is changeable.

  • 0
    TI__Genius 12395 points

    Hi Cho,

    Thank your for your post. A good rule of thumb for me is to have input bias current at 1000x less than what I am measuring. 

    Below is the 5V example of input bias current change as a result of common mode voltage. Please keep this in mind; as the common mode increases, so does the Ibias. 

    I do not see an issue with the shunt, Isense, or supply voltages you have provided for the INA199.

    Are you running into any issues with your design or circuit?

    CHO SR said:
    Rshunt to detect 20mA is changeable.

    Do you mean that the 20mA sense is not a strict design requirement? I would like some clarification on what you mean by changeable.

    Best Regards, 

    Joe

  • 0 in reply to Joe Vanacore
    Genius 3225 points

    Hi Joe,

    Sorry, I made a mistake in writing the case.

    There is no problem with the circuit.

    Customer wanted to check before design the schematic.

    The customer's question is whether 20mA detection is possible with this condition.

    Supply : 9V ~ 18V

    Rshunt : 0.05ohm

    If the Rshunt value is not 0.05 ohm, it means it can be changed.

  • +1 in reply to CHO SR
    TI__Genius 12395 points

    Hi CHO,

    No worries for the mistake. I do not see an issue and also please note the input bias current comment I provided.

    I will now mark this as resolved. As the design progresses, please reach out for additional support.

    Best Regards, 

    Joe