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  • TI Thinks Resolved

DRV5055: DRV5055

Prodigy 50 points

Replies: 4

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Part Number: DRV5055

Hello,

My name's Abdoul and I have a few questions about TI's linear hall effect sensor (DRV5055). We want to use a combination of the hall sensor with an appropriate magnet placed on a float to determine fill level of a liquid inside a container. The datasheet mentions that the linear magnetic sensing range for the DRV5055A4 is +/- 176mT, is there a way we can determine the proper magnet (size, magnetic strength, etc.) that should be used in this case and also what the minimum distance between magnet and sensor should be? 

Thank you

  • Abdoul,

    Right now our calculator tool that should be on the DRV5055 landing page is not available.  I'm working to get that corrected.  It would normally allow you select a few grades of magnets and shapes.  It would then allow you to enter a distance along the axis of polarization and would provide a B field value.

    As an alternative while this is unavailable, you might try using this tool available from K&J magnetics, 

    https://www.kjmagnetics.com/fieldcalculator.asp

    This one at integrated magnetics,

    https://www.intemag.com/on-line-calculators-i-21.html

    Another at Adams Magnetic Products,
    https://www.adamsmagnetic.com/gauss-and-pull-calculators-magnets

    or you could do a more detailed simulation in FEMM (Finite Element Method Magnetics)

    http://www.femm.info/wiki/HomePage

    Thanks,

    Scott Bryson

  • In reply to Scott Bryson:

    Thanks Scott for the information. I have another question concerning the full-scale magnetic sensing range (BL) of the DRV5056. Does BL represent the maximum or minimum magnetic strength that results in saturation? For the DRV5056A4, BL is 158mT with Vcc=5V at 25C  

  • In reply to Abdoul Bah:

    Abdoul,

    BL is the minimum field strength that may result in saturation. It is a function of the Maximum Sensitivity (S), maximum voltage in the linear output region of the device (Vl), and the maximum value of the quiescent output voltage (Vq).  

    For example with the DRV5056A4 package, Sensitivity has a maximum value of 15.8 mV/mT when operating at 3.3 V (Smax = 26.2 mV/mT at 5 V).  If we apply 155 mT (BL min), then our expected output will be 2.45 V above the quiescent voltage of 0.65 V. The resulting output voltage would be about 3.1 V which is 0.2 V below Vcc (VL max).  Beyond this and the output is not guaranteed to be linear as the output starts to saturate. 

    Thanks,

    Scott 

  • In reply to Scott Bryson:

    I see, it makes sense. Thanks Scott!

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