TMAG5123: 2 ~ 4 mm distance, any design consideration ?

PYTSai,

Thanks for reaching out on E2E.  The main goal when designing with a switch is to consider that you should see a change in magnetic flux density that will span BOP Max and BRP Min.  Suppose you selected TMAG5123B

Here you should see switching across all configurations if you can ensure that the field magnitude in the sensitivity direction varies > 6 mT at the closest position and <0.3 mT at the furthest position.

Also, because this device is omni-polar it will toggle with either positive or negative fields.  If the motion of the magnet is able to create a field magnitude in the opposite direction which exceeds 2.2 mT then it would be possible to get a second trigger event.

I would recommend using the TI Magnetic Sense Simulator to model your design and try out different magnet options and configurations:

https://webench.ti.com/timss/

Thanks,

Scott

The Hall element location in TMAG5123 is shown here:

When placing the device in TIMSS, the tool will position the package relative to the center point of the footprint on the PCB surface.  The location of the sensing element is adjusted for based on this location.

Thanks,

Scott

PYTsai,

One quick note.  The device you have selected is an omni-polar switch type output.  For motor commutation we normally expect to see latches, such as TMAG5115. The difference being that latches switch their output only after the opposite pole is presented, where an omnipolar switch will toggle if the field magnitude (positive or negative) ever exceeds a minimum value.

Assuming TMAG5123 is still what you want, I went ahead and setup TIMSS with the sensor location accounted for and with two additional devices rotated by 120 degrees.  The method for this placement can follow this process for any device, but is shown below using TMAG5123:

1. Determine the sensing element location relative to the device package
   1. Width = 1.3 mm , Length = 2.92 mm
   2. Center = (0.65 mm, 1.46 mm)
   3. Element location = (0.605mm, 1.765 mm)
   4. offset from center (305 mm,-0.045) 
      1. Note: Length above corresponds to X for TMAG5123.  For most other devices in this package this parameter is in the Y direction.  
2. Determine radius from magnet center
   1. assume desired first sensor position at (r,0) where r is radius from magnet center and rotated aligned to magnet
   2. new position = (r+0.305,-0.045)
3. Place additional sensors at 120 degree rotation
   1.  sin(120)  =  ½√3     ,  sin (-120)  = -½√3
   2. cos(120)  = -½         , cos (-120)  = -½
   3. coordinate rotation formulae
      1. X' = X*cos(Θ) - Y*sin(Θ)
      2. Y' = X*sin(Θ) + Y*cos(Θ)
   4. X2 = (-½(r+0.305))        - (0.045 * ½√3)
   5. Y2 = ((r+0.305) * ½√3)  - (½ * 0.045)
   6. X3 = (-½(r+0.305))        - (0.045 * -½√3)
   7. Y3 = ((r+0.305) * -½√3) - (½ * 0.045)
4. Suppose r = 5. Coordinates are shown below:
   1. (-2.61353 , 4.61676)
   2. (-2.69147 , -4.61676)

Here is an example script which you can load into TIMSS

{
  "version": "2.0.1",
  "design_name": "",
  "magnet_id": 2,
  "poles": 2,
  "material_id": 1,
  "grade_id": 1,
  "select_remanence": "br_average",
  "remanence": 1200,
  "temperature": 20,
  "temperature_coefficient": -0.12,
  "coercivity": 10.9,
  "function_id": 4,
  "magnet_geometry": {
    "outer_diameter": 6,
    "height": 3
  },
  "magnet_position": {
    "x_position": 0,
    "y_position": 0,
    "z_position": 0
  },
  "magnet_angle": {
    "x_angle": 0,
    "y_angle": 0,
    "z_angle": 0
  },
  "magnet_movement": {
    "arc_length": 360
  },
  "sim_setting": {
    "angular_step_size": 0.25
  },
  "sensor": [
    {
      "sensor_id": "TMAG5123-Q1",
      "sensor_position": {
        "x_position": 5.305,
        "y_position": -0.045,
        "z_position": 0
      },
      "sensor_angle": {
        "x_angle": 0,
        "y_angle": 0,
        "z_angle": 0
      },
      "custom_inputs": {
        "variant": "TMAG5123D1CEDBZRQ1",
        "applied_vcc": 3.3,
        "bop": "bop_typ",
        "brp": "brp_typ"
      },
      "id": -1
    },
    {
      "sensor_id": "TMAG5123-Q1",
      "sensor_position": {
        "x_position": -2.61353,
        "y_position": 4.61676,
        "z_position": 0
      },
      "sensor_angle": {
        "x_angle": 0,
        "y_angle": 0,
        "z_angle": 120
      },
      "custom_inputs": {
        "variant": "TMAG5123D1CEDBZRQ1",
        "applied_vcc": 3.3,
        "bop": "bop_typ",
        "brp": "brp_typ"
      },
      "id": -2
    },
    {
      "sensor_id": "TMAG5123-Q1",
      "sensor_position": {
        "x_position": -2.69147,
        "y_position": -4.57176,
        "z_position": 0
      },
      "sensor_angle": {
        "x_angle": 0,
        "y_angle": 0,
        "z_angle": -120
      },
      "custom_inputs": {
        "variant": "TMAG5123D1CEDBZRQ1",
        "applied_vcc": 3.3,
        "bop": "bop_typ",
        "brp": "brp_typ"
      },
      "id": -3
    }
  ]
}