• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 49 subscribers
  • Views 652 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

INA 226 Current Measurement

ELEANOR
Prodigy 10 points

Other Parts Discussed in Thread: INA226

Hi,

I am using INA226 in my design to measure the current consumption in the high side current sensing mode. Load current will be in the range of .06uA to 50mA from sleep to active mode of operation. The Bus voltage will be in between 3-3.6 V

I am now using 50 milli Ohm current shunt resistor in the design. In one of the other blogs, with this much resistance I can get  50uA resolution in the measurement.

I want to know, what is the lowest possible current that can be measued with what much accuracy if I can change the current sense resistor value? 

  • 0
    TI__Expert 6930 points

    Hi Eleanor,

    Thank you for your question regarding the INA226 and low current measurement capability...in your application I understand that you are trying to measure a current as small as 60nA.  The input bias current to the INA226 is given as 10uA (typ) and can vary based upon the specific operating conditions...this input bias current is many times larger than your desired minimum signal and therefore a large error will result.  We can probaly assume that you would have a minimum of 10% error if you had a minimum current of 100uA...if your minimum current was 1mA then due to the input bias current your error would be around 1% plus any error due to offset voltage, gain error and common mode rejection etc.  Your application sounds better suited for a traditional instrumentation amplifier...a traditional instrumentation amplifer has very high imput impedance with very low input bias current.  Perhaps if you can share some additonal information on your application we can make a recommendation other than INA226...here are a few basic questions that would be helpful for us to understand to make the best recommendation to you:

    • What power supply rails are available in the system?
    • What is the Common Mode Voltage range over which your application will operate over?
    • I understand that your input current range is from 60nA to 50mA
    • How much voltage drop can you tolerate across the shunt resistor at full scale current?
    • What accuracy do you require for your application?
    • Over what temperature range will your application operate?
    • What is the expected frequency range for the load current to be measured?
    • Do you have a specific resolution for the current measurement in mind? 12 bit, 14 bit, 16 bit?