HAL855
DATA SHEET
Step 4: Calculation of Shift and Slope
2.3.2. Example: Calibration of an Angle Sensor
Set the system to calibration point 1 and read the
register DIGITAL OUTPUT. The result is the value
DOUT1.
The following description explains the calibration pro-
cedure using an angle sensor with a HAL855 as an
example. The required output characteristic is shown
in Fig. 2–5.
Now, set the system to calibration point 2, read the
register DIGITAL OUTPUT, and get the value DOUT2.
– the angle range is from −25° to 25°
– temperature coefficient of the magnet: −500 ppm/K
With these values, the settings for Sensitivity and Shift
are calculated as:
(DOUT2NOM – DOUT1NOM
)
--------------------------------------------------------------------------
×
Slope = SlopeINITIAL
%
HAL855
(DOUT2 – DOUT1)
100
Second Calibration Point
Output
Duty
Cycle
90
80
70
60
50
40
30
20
100%
-------------
(DOUT2 – 2048) × Slope
----------------------------------------------------------------
× DOUT2NOM –
Shift =
4096
SlopeINITIAL
Write the calculated values for Slope, Shift, and the
desired output characteristic into the EEPROM. The
sensor is now calibrated for the customer application.
As long as the LOCK bit is not set, the calibration pro-
cedure can be applied repeatedly.
Linear
Sine
Note: For a recalibration, the calibration procedure
has to be started at the beginning (step 1).
A new initialization is necessary, as the initial
values for SlopeINITIAL, ShiftINITIAL and output
characteristic are overwritten in step 4.
First Calibration Point
10
°
-30
-20
-10
0
10
20 30
Angle
Linear
Fig. 2–5: Example for output characteristics
0
Sine
Step 5: Locking the Sensor
The last step is activating the LOCK function with the
“LOCK” command. Please note that the LOCK function
becomes effective after power-down and power-up of
the Hall IC. The sensor is now locked and does not
respond to any programming or reading commands.
Warning: This register cannot be reset!
14
Nov. 26, 2008; DSH000149_003EN
Micronas
MICRONAS [ MICRONAS ]
