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INA226-Q1 How to use (cont)

na na78
Guru 16770 points
Other Parts Discussed in Thread: INA226-Q1, INA226

Hi


We are sorry that we made bad posting (multiple posting) in following thread and unwillingly we couldn't no longer add questions for moderation)

If possible, please allow us to continue questioning in this thread?

- INA226-Q1 How to use    

1. We got the gain error. Can we refer the offset errors?

2. Thanks. We got it.

3. We have to apologize for our confusing figure. We supposed 2 loads and a shunt. Anyway, we wanted to know the difference of voltage between VBUS and GND could be measured even if GND pin was not connected to ground. That is impossible, isn't it?

4. Shunt current and bus voltage is sampled by ADC automatically and that can not be controlled, isn't it?

5. Thanks. We got it.

6. Is the capacitance 3 pF you mentioned the input capacitance of ADC? Do you have the information about input impedance?

Please let us add questions.

7. Can we select the any Rshunt so that the input voltage of INA226 is in the shunt voltage input range?

8. The specifications on the datasheet are described for Vvs=3.3V.  If Vvs=5V, are there any considerations?

9.  Can we refer the maximum value of Input bias current over temperature?

10. What is the voltage source for generating the reference voltage of ADC, Vbus or Vvs? We are assuming the Vbus is open.

Best Regards

  • 0
    TI__Genius 15760 points
    Hi Na na,

    I will review your new questions on Monday.

    Mayrim
  • 0 in reply to Mayrim Verdejo
    Guru 16770 points
    Hi Mayrim

    Thank you for your review.
    We appreciate your help if you have had information.

    BestRegards
  • 0
    TI__Genius 15760 points

    1. You can refer to Vos spec of the datasheet.
    3. I don't believe that is possible. I share this with one of my co-workers and he have not seen this configuration before either.
    4. You can set bus voltage and shunt voltage conversion times on the INA226. Refer to Page 23 of the datasheet.
    6. Input capacitance that you see on the I2C lines. Input impedance, I dont have that number.
    7. Yes. Just make sure you stay uinder specs. Refer to this video for guideline. training.ti.com/getting-started-current-sense-amplifiers-session-4-how-choose-appropriate-shunt-resistor
    8. What are the parameters that you are concerned about? e have a training video series that can help you understant the different types of errors in our INAs. Please refer to this as well so you get an idea/understanding. e2e.ti.com/.../467332
    9. Figure 13 of the datasheet shows the Input Bias current value vs Temperature.
    10. I don't understand this question. Vs is the supply voltage of our INA226. Vbus is the voltage detected in the bus. 

    Hope this helps!

  • 0 in reply to Mayrim Verdejo
    Guru 16770 points
    Hi Mayrim

    Thank you for your reply.
    If possible, could you please give me comments for the following?

    6. Input capacitance that you see on the I2C lines. Input impedance, I dont have that number.
    -We understood there is no information about ADC input impedance and capacitance.

    9. Figure 13 of the datasheet shows the Input Bias current value vs Temperature.
    -Thanks, we checked it out. The input bias current seems 10uA according to electrical characteristics but that can not be recognized from Figure 13. How to get the typical value of input bias current 10uA?

    10. I don't understand this question. Vs is the supply voltage of our INA226. Vbus is the common mode voltage.
    -I'm sorry my question was not good. We think the ADC in INA226 would need the reference voltage to work.
    So we wanted to confirm if the ADC can work properly for sensing shunt voltage and current when Vbus is open.

    Best Regards
  • 0 in reply to na na78
    TI__Genius 15760 points
    Hi na na78,

    9. The numbers do not match. Allow me some time to review characterization data and let you know what the correct number is. I would say use the graph as your reference while I research about this.

    10. Yes. You can sense shunt voltage and current when Vbus is open.
  • 0 in reply to Mayrim Verdejo
    Guru 16770 points
    Hi Mayrim

    Thank you for your reply.

    >9. The numbers do not match. Allow me some time to review characterization data and let you know what the >correct number is. I would say use the graph as your reference while I research about this.
    Thanks. We'll wait for the answer.

    BestRegards
  • 0 in reply to na na78
    TI__Genius 15760 points
    Hi na na78,

    The Input Bias Current specified on the Electrical Characteristics section is correct: Ib = 10uA (typical). We look at the characterization data and found out the curve shows Ib+ added with Ib-. This graph is based on total Ib.

    Regards,
  • 0 in reply to Mayrim Verdejo
    Guru 16770 points
    Hi Mayrim

    Thank you for your help.
    I would like to close this thread.

    BestRegard