• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 171 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMAG5273: Questions about TMAG5273

Zach Zhu
Intellectual 1490 points
Part Number: TMAG5273

Tool/software:

Hi,

Customer is developing control handle using TMAG5273. Could you pls help answer question? Thank you!

1.If the SMT device is offset, what will be the impact on the B value? How to verify it during mass production?

2. How to understand update rate?

3. How to understand sensitivity option and temp compensation

4. Are temperature sampling and flux sampling performed simultaneously? Is temperature sampling necessary?

5. How to select magnet? How to understand Magnetic Limit Check?

6. How to understand Magnetic Tamper Detection? 

BR,

Zach

  • 0
    TI__Mastermind 26335 points

    Hello Zach,

    1.  The direction the offset, size of offset, relative distance to the magnet all have impact.  If the magnet is nearby, offset can change dramatically, if the magnet is far away, not so much.  To get an idea of how it would affect the field detected by the TMAG5273 in your system, I would suggest using our TIMSS tool. (https://webench.ti.com/timss/)

    2.  The device has sequential sampling and averaging.  For instance, if you choose to get measurement from just x and y channel, that should take 50us+25us=75us for one set of measurements  (first sample of the measurement cylce takes 25us longer).  From that if you you 1s/75us = 13.3k, similar to what is observed in table 6-4 of the datasheet.

    3.  Sensitivity is related to sensing range and resolution with greater sensitivity equating to less range or a smaller max field. For an example, lets assume your max expected field is 32.05mT (TIMSS can help you determine that value).  We could devices with a range of 40mT, 80mT, 133mT, or 266mT range.  All have the same number of possible measurement codes, but those codes would translate to different resolutions. If we take 32.05mT/(1/SENS) where SENS is LSB/mT, we see how many bit correspond to 32.05mT.  In this case it would 26281, 13140.5, 8012.5, and 4006.25.  As we can't have a fraction of bit, only the 40mT option has sufficient resolution to actually measure 32.05mT.  As the allowable measurement range increases, less sensitivity is needed, and as the internal ADC is still only 12 bits, the resolution scales with the range to coarser steps.

    For temperature compensation I would do SENS(1+MAG_TEMPCO(%/°C)*(Temp°C-25°C))

    4. Temperature compensation occurs so long as it is selected regardless of whether temperature is sampled or not.  Those measured values are sampled in sequence. Temperature sampling may be useful if you decide to do compensation through postprocessing of the data or if you are hoping to get a relative temperature value for some other extremely close component.

    5. I would recommend iterating through a design in TIMSS for determining relative magnet size.  Otherwise magnet selection can be guided by mechanical space constraints, mechanical durability and cost.

    6. Assuming you use more than one sensing axis, for a characterized system with deterministic magnet movements you should know what the sensor should typically detect.  For example with a linear magnet movement,  you might expect the X-channel to exhibit a linear output while the Y-channel is roughly 0mT for all values.  Therefore, if during operation you see a significantly large Y-channel reading for any given X-channel reading you can either assert the position sensing module is broken or someone or something has introduced a tampering field.