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Original question:

INA225: About INA225's internal resister

INA225: INA225-Q1 current consumption.

Wentao Zeng
Prodigy 590 points
Part Number: INA225

My customer want to know the current consumption.  

VCC:5V,   Input:+/-70mV, output: +/-1.7V, We will measure bidirection current using Reference.

ADC input impedence:It is very big  value becasue of input amplifier .

Now we know Quiescent current is 250uA when input=0V.


Could you give some suggestion following parameter consumption?  VCC:5V,   Input:+/-70mV, output: +/-1.7V,

  • 0
    TI__Mastermind 32395 points
    Hello Wentao,

    To consider power (current) consumption of INA225 or any other current sense amplifier, you will also need to factor in what the common-mode voltage (VCM) at input pins will be. Also customer needs to factor in any resistive loads to ground on the output of the INA225. A resistor from OUT to GND will add an output current to the total current consumed by the device.

    The input differential voltage of +-70 mV will increase the current going into IN+, but this current will come back out of IN-. This happens because there is an effective internal differential resistance (Rdiff) from IN+ to IN-. So technically this will be a resistance in parallel with the shunt resistor and this won’t actually contribute to the net current consumed INA225. You can actually calculate Rdiff = Vsense/(IB+ minus IB-). I calculate Rdiff = 1.1 kOhms using data from the application note: Power Saving Topologies for TI Current Shunt Monitors. See link here:
    www.ti.com/.../sboa180a.pdf

    I would recommend using this application note. This document shows extensive data on how current is consumed by our sensors. With it customer could possibly see data for their specific application. From this app note customer can see difference in IQ when REF is GND or Vs/2 ( mid-supply). IQ will always be higher when the device is ground referenced. I calculate that IQ increases somewhere in between 9.4 microamps to 13.4 microamps when you shift REF from mid-supply to ground when VS=5V. I calculated this using the application note above.

    So if customers bus voltage is 12 V and there is no output load, I would calculate total current consumed with :

    Itotal,max = IQ,max + 2*IB,max + 13.4 microamps.

    Where IQ,max = 350microamps
    IB,max = 85 microamps at Vcm = 12V.
    13.4 microamps is the increase to IQ when part is ground referenced.

    So Itotal,max = 533.4 microamps.

    Note that the complete equation would include output current and temperature effects, which can be deduced from the data sheet.

    Best,
    Peter Iliya
    Current Sensing Applications