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INA236: Using the INA236 for in-line H-Bridge Current sensing

Hugh Jeremy
Prodigy 10 points

Part Number: INA236
Other Parts Discussed in Thread: DRV8220, , INA240

I am investigating designing a high precision valve driver using the DRV8220 (DRL) and need to implement current sensing to be able to control the valve position. The driver should be able to control valves which take +/-10mA to +/-100mA for positional control.

I see that the datasheet for the DRV8220 outlines current sensing can be implemented by putting the sense resistor on the ground pin, however I worry this will lead to inaccuracy in the results as I presume the current for the chip itself will also be fed through this sense resistor.

I came across Current Sensing in an H-Bridge which outlines various analogue INA devices that can be used for high, low or in-line measurement. However, I would prefer to use an I2C device. Is the INA236 (and family) suitable for my in-inline (bidirectional) use?

To summarise my questions:

  • Is the DRV8220 suitable for these relatively low current driving applications?
  • Is the sense resistor to ground of the DRV suitable for precision measurement?
  • Is the INA236 suitable for in-line measurement?

Regards,

H

  • 0
    TI__Genius 10300 points

    Hi Hugh,

    Hugh Jeremy said:
    Is the DRV8220 suitable for these relatively low current driving applications?
    Hugh Jeremy said:
    Is the sense resistor to ground of the DRV suitable for precision measurement?

    There is a dedicated DRV team that can give you the best response, I will add them to the thread.

    Hugh Jeremy said:
    Is the INA236 suitable for in-line measurement?

    No, the INA236 does not have built in PWM rejection like the INA240 or INA241. However, you can use the INA236 for high-side measurement.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    Prodigy 10 points

    Hi Mallika, 

    Thanks for the quick response. When using the INA236 in high-side measurement, would I not end up measuring the power of the DRV8220 as well - the datasheet for that chip notes it has a 2mA active mode current which would be 20% of my intended driver current. I assume this would make precision control extremely difficult.

    Are there inline capable chips which have an I2C output, or should I reconsider my design to use something from the line of analogue current monitors - ideally I want something small to keep the overall design size to a minimum.

    Regards,

    H

  • +1 in reply to Hugh Jeremy
    TI__Genius 10300 points

    Hi Hugh,

    You're right, that is the caveat for high side sensing. 
    Unfortunately we don't have a digital output device for in-line sensing at the moment, I would recommend using the INA240 or INA241 and then digitizing the output. 

    Best,
    Mallika Senthil