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ina226: ina226

Part Number: INA226
Other Parts Discussed in Thread: TIDA-01608, TIDA-00313

I will use ina226 negative voltage

Is this schematic is correct?

Please give me inform.

  • Hello user5279670,

    Overall this schematic appears reasonable. I compared it with our "-48V Telecom Current/Voltage/Power Sense with Isolation" reference design and it looks pretty similar except that you are making the INA226 ground the same as the ground of the system you are monitoring (-10V). If you are looking for different ways to accomplish this type of circuit, you could also look into an upgraded isolated current sensing design (TIDA-01608, see below).
    www.ti.com/.../TIDA-00313
    www.ti.com/.../TIDA-01608

    Two things I am unsure on are what the -28V rail is for and why decoupling the supply pin (VS) to it is necessary and the second thing is what your load is. Are you connecting Vin- to the -10V rail?

    Sincerely,
    Peter Iliya
    Current Sensing Applications
  • Hi.

    VBUS Power Rail and VS+ Power Rail is seperated.

    VS+ Power is fixed -10V.

    VBUS Power vary -1V ~ -9V. Is voltage range right?

    Best Regards,

  • Hello user5279670,

    Thanks for you answers. Yes this voltage range for the VBUS pin is within the proper range.

    Sincerely,
    Peter Iliya

  • Hi.

    VBUS Sensing Voltage is fixed at -10V though VBUS vary -1V ~ -9V.

    What shall I do for this problem?

    Best Regards,

  • Hello user5279670,

    As mentioned in TIDA-00313 design documentation, the VBUS pin has an internal 830 kOhm resistor connected to the INA226 GND pin. This is how the VBUS measurements are made inside the INA226. So if you want to get any type of voltage reading you need to make sure that the VBUS voltage > GND voltage, which for your case it is (-9V > -10V and -1V>-10V). You also want to make sure VBUS does not get to high so ensure that VBUS<(GND_INA226+40V) or VBUS<30V since your GND is at -10V. Why not connect VBUS to the high-side of your load?

    I am confused about what your problem really is and why according to your schematic that Vin- can vary from -1V to -9V. Your Vin- pin seems to be directly connected to GND (or -10V rail) so Vin- and Vin+ are always going to be near -10V. This is your common-mode voltage and thus your are really in a low-side configuration. Furthermore, you have your VBUS pin connected to Vin+ below your load so I am not sure how your VBUS pin will actually sense a varying load voltage.
     
    Please provide some more schematic information and problem description.

    Sincerely,
    Peter Iliya
    Current Sensing Applications