HAL856 Datasheet, PDF (14/42 Pages) Micronas – Programmable Linear Hall-Effect Sensor with Arbitrary Output Characteristic (2-Wire)

HAL 856
DATA SHEET
Step 2: Initialize DSP
As the DIGITAL OUTPUT register value depends on
the settings of SLOPE, SHIFT and the OUTPUT
CHARACTERISTIC, these registers have to be initial-
ized with defined values, first:
– Shift_INITIAL = 50%
– OUTPUT CHARACTERISTIC = ’Linear Standard’
(Setpoint 0 = 0, Setpoint 1 = 16, Setpoint 2 = 32, ...,
Setpoint 31 = 496).
– Slope_INITIAL depends on the setting of the digital
low-pass filter (see Table 2–9).
Table 2–9: Initial slope values
−3 dB Frequency
80
160
500
1000
2000
Slope_INITIAL
0.2578
0.2578
0.1938
0.1938
0.3398
Step 3: Define Calibration Points
For highest accuracy of the sensor, calibration points
near the minimum and maximum input signal are rec-
ommended.
Define nominal values DOUT1_NOM and DOUT2_NOM of
the DIGITAL OUTPUT register at the calibration points
1 and 2, respectively.
Note: Micronas software PC856 uses default settings
DOUT1_NOM = 0 and DOUT2_NOM = 3968.
The output is clamped to Setpoint 0 and
Setpoint 31. In the case of “Linear Standard’”,
Setpoint 0 corresponds to DIGITAL
OUTPUT = 0, while Setpoint 31 corresponds to
DIGITAL OUTPUT = 3968.
Step 4: Calculation of Shift and Slope
Set the system to calibration point 1 and read the
register DIGITAL OUTPUT. The result is the value
DOUT1.
Now, set the system to calibration point 2, read the
register DIGITAL OUTPUT, and get the value DOUT2.
With these values, the settings for Sensitivity and Shift
are calculated as:
Slope
=
S
lo
pe_I
N
I
T
I
A
L
×
-⁽--^D-----^O----^U-----^T----2---^N---^O----^M------–----^D-----^O----^U-----^T----1---^N----^O---^M-----⁾
(DOUT2 – DOUT1)
Shift
=
1----0---0---%---
4096
×
⎛
⎝
DOUT2_NO
M
–
-⁽--^D-----^O----^U----_S-^T---_l-2-_o---_p^–----_e-2-_I--0_N---4-_I--_T^8---_I⁾-_A---^×-_L---^S----^l--^o---^p----^e-_⎠⎞
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.
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 Slope_INITIAL, Shift_INITIAL and output
characteristic are overwritten in step 4.
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
March 23, 2010; DSH000142_002EN
Micronas