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INA193A-Q1: Common Mode Volatge

hideyuki sakai
Mastermind 6250 points
Part Number: INA193A-Q1

Dear, Sir.

My customer is facing a strange symptom on INA193A-Q1 circuit.

Thay are applying 5V for V+(Vs). Rs = 10mOHM.

The load is FET(drain). INA193A-Q1 is measuring the current into FET.

They set the input floating, so Is = 0A.

Under above condition, Around 2V can be observed on both VIN+/VIN-  

pin when 5V was applying to V+(Vs).

Is it the normal behavior on INA193A-Q1?

Please give your advice.

Best Regards,

H. Sakai

  • 0
    TI__Mastermind 28840 points

    Hello Sakai,

    I think this is the same condition as seen on this post.  This has to do with the input bias current and if the current cannot be supplied externally then the part bias the voltage up. 

    Another thing to keep in mind is normally the device with under 20mV for the Vsense voltage does not work well depending on the Common mode voltage.  Here are some of the conditions described that are explained in the datasheet.  Section 7.4 goes into detail.  

    • Normal Case 1: VSENSE ≥ 20 mV, VCM ≥ VS
    • Normal Case 2: VSENSE ≥ 20 mV, VCM < VS
    • Low VSENSE Case 1: VSENSE < 20 mV, –16 V ≤ VCM < 0
    • Low VSENSE Case 2: VSENSE < 20 mV, 0 V ≤ VCM ≤ VS
    • Low VSENSE Case 3: VSENSE < 20 mV, VS < VCM ≤ 80 V