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INA213-Q1: Location of filter in INA213-Q1 to reduce noise

Oliver Kim7
Intellectual 2710 points
Part Number: INA213-Q1
Other Parts Discussed in Thread: INA213, OPA340, INA233, INA220, INA226, INA219, INA231, INA260

Dear team,

I use INA213-Q1 to measure amount of current.

I want to increase the Rs (See the figure) value more than 10 ohm because of the noise problem, but you know, it's not recommended because of the sensing accuracy problem.

Speaking of my opinion, how about moving the filter location to the output of INA213-Q1 and increase RC value to reduce noise?

I know this will increase INA213-Q1 output impedance but they use OPA340NA to drive voltage to ADC input.

I believe OPA340NA solves INA213-Q1 high output impedance issue even if the filter is located in the back side. What do you think about this?

  • 0
    Guru 140200 points

    Hi Oliver,

    when using the OPA340 I would filter at the input AND output of INA213. I don't see any problem. Rs at the input of INA213 should still be kept to <10R, though. At the output of INA213, on the other hand, the RC value can be increased, as the OPA340 has a very low input bias current.

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 27560 points

    Hi Oliver,

    The output can certainly be filtered to reduce noise. This is a logical choice especially when the desired filter is low bandwidth. In this case it will be difficult to implement equivalent filtering at the input. If signal bandwidth is low, then I would go with it. The drawback of course is the additional cost due to the buffer.

    You might also want to look into our line of digital output current sensing devices, such as INA226, INA219, INA220, INA231 and INA233. The beauty of this family of devices is that you can do effective filtering in the digital domain. Connect the I2C interface to existing controller and you’re almost there. I believe the cost will be lower than the analog solution. You can free up one ADC channel at the same time.

    You may also want to look into INA260, which is a digital output current sensor with integrated sense resistor.

    Regards, Guang

  • 0 in reply to Guang Zhou
    TI__Mastermind 27715 points

    Hi Oliver,

    It's been over two weeks since your last reply, so it seems like your issue has been resolved. I will close the thread for now, but if you have any further questions you can reply to re-open it, or start a new thread with a new question.

    Best regards,

    Ian Williams
    Applications Manager
    Current & Magnetic Sensing