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Original question:

INA240-Q1: current consumption

INA240-Q1: Input Current Consumption.

Jagannathan S
Prodigy 10 points
Part Number: INA240-Q1


Hi, 

I wish to know the what will be maximum current consumed by the IC "INA240-Q1"  if the Vsense= Max Voltage. Can anyone give the value for I (input)(max) ? 

regards, 

Jagan

  • 0
    TI__Expert 4720 points

    Hello Jagan,

    I have some confusion about your question. First are you looking for the current consumed by the IC or the Input bias current (Ib) or both? Second when you are referring to "Vsense = Max Voltage" do you mean the absolute max Vsense the IC can handle or the max recommended Vsense?

    Regards,

    Castrense

  • 0 in reply to Castrense Nigrelli
    Prodigy 10 points

    I am looking for current consumed by the IC. Yes, I mean the absolute max Vsense the IC can handle. 

  • 0 in reply to Jagannathan S
    TI__Expert 4720 points

    Hello Jagan,

    The maximum differential voltage the INA240-Q1 can handle on the input pins is +-80V.

    The input bias current at this voltage can be obtained by looking at fig. 33 of the INA240-Q1's datasheet.

    Using the graph, we are able to calculate the differential input impedance of the INA240-Q1.

    Calculation of differential input impedance:

    Using the graph, we can see at .8 Vdiff (differential input voltage) the Ib (input bias current) = ~220uA

    Using the graph again we see at .2 Vdiff the Ib = ~120uA

    Using these numbers and V=IR the Rdiff (differential input impedance) = (.8-.2)/((220-120)*10^-6) = 6 kOhms

    Calculation of I (current):

    Taking this measurements to the limits of the Vdiff we can see Ib+ = 80/(6*10^3) = 13.3 mA. While Ib- = -80/(6*10^3) = -13.3 mA

    We are extending the lines of fig. 33 all the way out to 80V.

    If there is no load connected to the IC, the Is (current consumed by Vs) = typ 1.8 mA with worst case being 2.4 mA.

    Taking a common mode voltage of 12 V will give us ~ 80 uA using fig. 14 on the data sheet

    Summing the currents 13.3 mA + 2.4 mA + 80 uA = 15.78 mA

    The IC is estimated to consume 15.78 mA with no load attached.

    There is a 20%-30% variation on the input impedance value.

    Keep in mind that the derivation of this value with particular care on the Ib+ and Ib-, is under the assumption the fig 33. is linear all the way to +-80 V differential.

    This assumption was made because some devices tested showed this behavior.

    We only guarantee values listed in the EC table of the data sheet.

    Let me know if you have any questions.

    Regards,

    Castrense