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DRV5053: Is a diode needed on each sensor if all of their outputs are connected in parallel?

Oskar Lenschow
Prodigy 70 points
Part Number: DRV5053
Other Parts Discussed in Thread: DRV5056, DRV5057, DRV5055

Hello! 

I want to create a matrix of multiple analog hall effect sensors using the DRV5053, and I want to power each column individually and then read  the output value per row (TimeOn is small enough to not be a problem in my case). This is to build a keyboard with 61 keys, which is why I want to power them this way. (They could all be powered all the time and then opened with transistors, but this feels like unnecessary power consumption.)

As I am quite new to reading diagrams and schematics, I might have missed the answer in the datasheet. But my question is this:

If all sensors on a row have their OUT shorted with each other, but only one of them is powered, as power is by column and not row, would the output value from the powered sensor go in through the OUT of the unpowered neighboring sensor and short to ground or something like that? Is there built in protection like a diode, or do I need to add diodes to each OUT?

Thanks for the help!


  • 0
    TI__Mastermind 26215 points

    Hello Oskar,

    Thank you for using the TI forum.  I will look into this question, and will get back to you by the end of the day tomorrow.  

    In the meantime, I would like to point out that the DRV5053 is one of our older linear Hall sensors. It has lower current consumption and higher voltage options than our newer versions (DRV5055, DRV5056, DRV5057), but is less accurate.  Also, if you only need to respond to one magnetic pole, then you may want to consider using a unipolar linear Hall sensor (DRV5056).

    I will check into your question for both the older and newer parts.

  • 0 in reply to Mitch M
    TI__Mastermind 26215 points

    Also,  when you are powering down the device, are you leaving VCC/GND pins floating or are they at 0V?

  • 0 in reply to Mitch M
    Prodigy 70 points

    I was planning on powering down to 0V on both ground and VCC pins.

  • 0 in reply to Mitch M
    Prodigy 70 points

    T-ON for the newer models also seems to be significantly higher than on the older model, which is not ideal.

  • 0 in reply to Oskar Lenschow
    TI__Mastermind 26215 points

    Oskar,

    Ok, so it sounds like the DRV5053 would be best for you.

    If you connect the outputs of the sensors together directly, and have VCC/GND at 0V for the off devices, then the output of the on device will essentially try to turn on the off devices due to some ESD diodes. This will cause the configuration to not work properly. 

    The best option would be to use switches/multiplexers on the output of the devices to select which one you want to use.  If that does not work for you, then you can technically use a diode on the output of each device, but that will cause a 0.7V shift in the output, which will also make the lower 0.7V part of the output range unusable (which might work for you if you only plan to only use one magnetic pole).  The diode will also introduce it's own temp co into the output voltage.

  • 0 in reply to Mitch M
    Prodigy 70 points

    I'm guessing you mean I would use 8 x 8ch analog multiplexers, so I have one per row and then I read the chosen value for each? Sounds like a pretty good idea, do you have a specific product that could work for me?

    I guess the ideal would be something like a 64ch analog multiplexer that I could wire every single sensor too, but seems like that might be rare?

  • 0 in reply to Oskar Lenschow
    TI__Mastermind 26215 points

    Hello Oskar,

    Yes, you would likely need multiple devices for your system.  Each Hall output would need to be the input to a switch/multiplexer, then you could even take the output of those switches/multiplexers and put them into another switch/multiplexer so that you only have one line with the signal on it.  

    TI has many switches an multiplexers. Here is the TI product overview page for analog switches and multiplexers: here:http://www.ti.com/switches-multiplexers/analog/overview.html.  

    If you would like help finding a specific switch/multiplexer that would go best with your system, I recommend posting on the Switches & multiplexers forum.  The easiest way to do that would be to click the "+ Ask a related question" button, then make sure that the forum is set to "Switches & multiplexers forum".  This way, the new forum post will link back to this one for more details.

  • 0 in reply to Mitch M
    Prodigy 70 points

    Okay, thanks a lot for all the help!