AK8996 Datasheet, PDF (45/74 Pages) Asahi Kasei Microsystems – Pressure Sensor Interface IC

[AK8996/W]
7) Offset Temperature Primary Characteristics (Compensation Procedure)
If the offset temperature drift first order coefficient is left over after adjustment of the sensor
characteristics, follow the readjustment procedure. Ensure that this procedure is conducted before
9. Offset Voltage Fine Adjustment.
Readjustment Procedure (See the figure below)
1. On the most recent setup of the adjustment temperature (e.g., at 50ºC), calculate the coefficient to
be applied to the AK8996.
2. After setup, measure the VOUT pin voltage (Voff50) with the pressure set to 0kPa.
3. Store the measured value in the memory (e.g., address 16 hex EUE[7:0]).
4. Restore the temperature to 25ºC (last adjustment phase).
5. Measure the VOUT pin voltage (Voff25) with the pressure set to 0kPa.
The adjustment procedure is normally completed with the adjustments of the offset voltage, pressure
determination threshold, output reference voltage and output span voltage fine adjustment. If,
however, offset temperature characteristic first-order coefficient needs to be adjusted, the following
adjustments should be performed first:
6. Calculate the remaining offset temperature characteristic first-order coefficients.
Remaining offset temperature characteristic 1^st order coeff. =
(Voff50-Voff25)/(50-25)[mV/ºC]···(A)
7. Calculate a gradient per step from the offset temperature drift first-order coefficient (e.g.,
0.04[mV/ºC]).
Adjustment code = (A)/0.04
8. Apply the calculated adjustment code to the OT1 register (address 06 hex).
Output
Output level for 0 kPa
with coeff. being applied
Output level with coeff
being applied
Voff25
0
25°C
Voff50
fine
tuning
50°C Temperature
Output level first set up
MS1055-E-02
45
2011/12