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INA293: Bandwidth and Slew Rate for Measuring AC Current in 1MHz Range

Yohzan Tanaka
Prodigy 10 points
Part Number: INA293
Other Parts Discussed in Thread: INA296B, INA296A

Tool/software:

Hello everyone,

I'm looking to measure AC current and observe its frequency characteristics up to 1MHz.
I've chosen the INA293 for this task, but as a beginner with little experience, I have three questions I'd like to ask:

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1. The slew rate is specified as 2.5V/μs. I understand this 2.5V refers to the change in output voltage. However, I'm worried this might be too low to follow a 1MHz signal, and I'm concerned I might be misunderstanding something. Am I correct in thinking this refers to the change in output voltage, not the change in Vsense?

2. From section 7.3.1.1 and Figure 7.1 in the datasheet, I've gathered that the bandwidth depends on Vsense, and a relatively large output voltage is needed for 1MHz bandwidth. Since I want to measure current in the 1MHz range, I tried to select a resistor that would fit within the 1MHz bandwidth range in Figure 7.1. I thought about using the method of replacing the Vsn part in Equation 3 with the minimum output voltage value that can achieve 1MHz bandwidth, as read from Figure 7.1, to determine the resistance value. Is this approach appropriate?

3. Could you please provide the specific output voltage values at which INA293x1, INA293x2, and INA293x3 reach the 1MHz bandwidth in the graph of Figure 7.1?

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The AC current I want to measure has a maximum value of 1A. Ideally, I'd like to be able to measure down to about 1mA at the minimum.
If there are any other ICs that might be better suited for this, I'd really appreciate your advice.

Best regards,
Yohzan.

  • 0
    TI__Mastermind 27800 points

    Hello Yohzna,

    Thanks for using E2E for answering your questions.  

    Yohzan Tanaka said:
    1. The slew rate is specified as 2.5V/μs. I understand this 2.5V refers to the change in output voltage. However, I'm worried this might be too low to follow a 1MHz signal, and I'm concerned I might be misunderstanding something. Am I correct in thinking this refers to the change in output voltage, not the change in Vsense?

    We have a video that covers Slew Rate vs bandwidth.

    Vidoe: https://www.ti.com/video/6310291491112#:~:text=Slew%20rate%20can%20be%20specified,for%20the%20small%20signal%20response.

    Presnetation: https://www.ti.com/content/dam/videos/external-videos/en-us/9/3816841626001/6310291491112.mp4/subassets/slew_rate_and_bandwidth.pdf

    Yohzan Tanaka said:
    2. From section 7.3.1.1 and Figure 7.1 in the datasheet, I've gathered that the bandwidth depends on Vsense, and a relatively large output voltage is needed for 1MHz bandwidth. Since I want to measure current in the 1MHz range, I tried to select a resistor that would fit within the 1MHz bandwidth range in Figure 7.1. I thought about using the method of replacing the Vsn part in Equation 3 with the minimum output voltage value that can achieve 1MHz bandwidth, as read from Figure 7.1, to determine the resistance value. Is this approach appropriate?

    Yes.  Getting a larger input voltage to meet your bandwidth requirements by increasing your Rshunt will work.  If this compromises your power you can increase the gain option or use our INA296 which has a higher slew rate as well of 8V/µs.

    Yohzan Tanaka said:
    3. Could you please provide the specific output voltage values at which INA293x1, INA293x2, and INA293x3 reach the 1MHz bandwidth in the graph of Figure 7.1?

    The plot is typical and exact values will vary from device to device.  I would use the graph and estimate the values.  If this is too big of a comprimise I would look at the INA296A or INA296B depending on your accuracy requirements.

    Regards,

    Javier

  • 0 in reply to Javier Contreras4
    Prodigy 10 points

    Hello Javier,
    Thank you very much for your response.
    I have one question, if I may.
    The INA296 datasheet does not mention any dependency between bandwidth and Vsense.
    For the INA296, does this mean there is no need to increase the output voltage to obtain bandwidth, unlike the INA293?