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DRV5057-Q1: Matching between DRV5057-Q1 and Alnico magnet

Seok Kim1
Intellectual 280 points
Part Number: DRV5057-Q1
Other Parts Discussed in Thread: DRV5057

Hello,
I am developing a brake system.
I am going to make a product that outputs a brake signal using a magnet and a hall sensor.

I am going to make a brake product that is resistant to heat.
However, while reading the datasheet, I have a question.

In the picture, it is indicated that the compatibility with nickel and cobalt is not good.

I was going to use the DRV5057-Q1 with Alnico magnet.
Can't Alnico magnets be used as indicated on the datasheet?

Does the DRV5057-Q1 calibrate even if the magnet density is changed?

There shouldn't be a problem because accuracy and reliability are so important.

Please let me know if what I understand is correct.

Regards,

  • 0
    TI__Genius 17190 points

    Hello,

    Thank you for your question.  This statement from the datasheet is specifically referring to the object which the magnet is attached to.  The point being that ferromagnetic materials (aside from the magnet itself) can cause unexpected changes to the magnetic field and therefore might change the anticipated field at the sensor.  Even when ferromagnetic materials are present, the device should still respond to changes in the component of the field vector which is directed through the Hall element.

    An AlNiCo magnet should still work with this device. There is not any self calibration built into DRV5057.  For example, any offset in magnet starting position will result in a change to the magnetic field and as a result the device will respond according to the change in observed field.  DRV5057 functions by adjusting the output PWM with respect to the applied magnetic flux density per this response:

    For temperature stability, it is important to consider the temperature drift of the magnet and that of the sensor.  The A1/A2/A3/A4 versions of the device have built in temperature compensation of +0.12%/C which is intended to counter the drift typical to NdFeB type magnets.  The drift of AlNiCo is much more stable than NdFeB, so it would most likely be better for you to consider using Z1/Z2/Z3/Z4 sensitivities which have a built in temperature drift of ~0%/C.