MLX90333
Triaxis 3D-Joystick Position Sensor
In summary, along X-axis, the left Hall plate measures “B
X⊥
- B
Z
” while the right Hall plate measures “-B
X⊥
- B
Z
”. Similarly, along the Y-axis, the left Hall plate measures “B
Y⊥
- B
Z
” while the right Hall plate measures
“-B
Y⊥
- B
Z
”.
Through an appropriate signal processing, the Tria⊗is™ sensor front-end reports the three (3)
components of the applied magnetic flux density B i.e. B
X
, B
Y
and B
Z
.
Indeed, by subtracting the signals from the two (2) Hall plates in each pair, the components B
X⊥
and B
Y⊥
are measured while B
Z
is cancelled. To the contrary, by adding the signals from the two (2) Hall plates in
each pair, the component B
Z
is measured while B
X⊥
and B
Y⊥
are cancelled
In a joystick based on a “gimbal” mechanism as shown on Figure 3 (left), the magnet (axial magnetization)
moves on a hemisphere centered at the IC. The flux density is described through the following
relationships:
B
X
=
SIN
(
α
)
⋅
COS
(
β
)
B
Y
=
COS
(
α
)
⋅
SIN
(
β
)
B
Z
=
COS
(
α
)
⋅
COS
(
β
)
Those components are plotted on the Figure 5, Figure 6 and Figure 7.
Figure 5 – Magnetic Flux Density – B
X
, B
Y
, B
Z
3901090333
Rev. Preliminary
Page 8 of 38
Data Sheet
May 07
MELEXIS [ Melexis Microelectronic Systems ]
