MA300GQ-P Datasheet, PDF (8/18 Pages) MPS Industries, Inc. – Angular Sensor for 3-Phase Brushless Motor Commutation and Position Control with Side-Shaft Positioning Capability

MA300
Angular Sensor for 3-Phase Brushless Motor
Commutation and Position Control with Side-Shaft
Positioning Capability
Figure 8: Hall Devices Biasing Diagram
If the MA300 is mounted in a side-shaft configura-
tion, the relationship between the field angle and
the mechanical angle is no longer directly linear.
This effect is related in that the tangential
magnetic field is usually smaller than the radial
field. We define the field ratio in equation (1):
(1)
where
and
are the maximum radial,
respectively, tangential magnetic field (see Figure
9).
255 (see Table 9). For optimum compensation,
the radial axis should be reduced by the quantity
in equation (2):
(2)
TABLE 9. EXAMPLE OF OPTIMUM BCT SETTING
BCT(7:0)
0
1
…
128
…
255
Magnet Ratio k
1
1.003
…
1.50
…
3.00
The dot printed on the package informs whether
the radial field is detected by sensor X or Y
components (see Figure 10).
Figure 9: Side-Shaft Field
8. Digital Signal Conditioning
The ratio k depends on the magnet geometry and
the distance to the sensor.
The X-axis or Y-axis bias currents can be reduced
to recover an equal Hall signal for all angles and
therefore suppress the non-linearity. The current
reduction is set by the parameter bias current
trimming, BCT (7:0), which is an integer from 0 to
Figure 10: Package Top View with X and Y Axes
First the user must determine which axis must be
reduced (see the qualitative field distribution
around a ring in Figure 9). For instance, with the
arrangement depicted in Figure 8, the X-axis
should be reduced. Then the parameter ETX or
ETY can be set. Note that if both ETX and ETY
are set to 1, the current bias will be reduced in
both directions the same way, i.e. without side-
shaft correction (see Table 10).
Monolithic Power Systems, Inc. | Gland, Switzerland | Tel: [phone] | [e-mail] | www.sensimatech.com
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Reserved. MA700 Rev 1.0 September 2014
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