AK8996 Datasheet, PDF (35/74 Pages) Asahi Kasei Microsystems – Pressure Sensor Interface IC

[AK8996/W]
Explanations for "Calculating Sensitivity Temperature Characteristics 2^nd Order Coefficients", "Offset
Temperature Secondary Characteristics Calculation Example" and "Sensitivity Temperature Secondary
Characteristics Calculation Example." are described in the following section.
■ Calculating Sensitivity Temperature Characteristics 2^nd Order Coefficients
The difference between the values measured at the VOUT pin for three temperature points and the
reference values at the reference voltage (Vbase = 0.8 V) is calculated to obtain the following coefficients
for the sensitivity:
Sensor: α ga, β ga, γ ga
AK8996: a, b, c (quadratic function output), d, e (linear function output)
For example, assume:
Sensitivity temperature drift measurement result for a sensor alone:
Vsenc (25ºC), Vsenn (low temp), Vsenp (high temp)
Sensitivity temperature drift measurement result for AK8996:
Vicc2 (25ºC), Vicn2 (low temp), Vicp2 (high temp) quadratic function
Vicc1 (25ºC), Vicn1 (low temp), Vicp1 (high temp) linear function
Note) These values are for the span from which the offset voltages are subtracted for each temperature.
1) The gain values (gc, gn, gp) for compensating the sensitivity temperature drift are obtained from the
sensitivity temperature drift results of a sensor alone:
gc=Vsenc/Vsenc=1, gn=Vsenc/Vsenn, gp=Vsenc/Vsenp
For the gain values (gc, gn, gp) obtained, find the voltage that should be output from the AK8996
quadratic function generator.
Vsenc1=Vbase/gc, Vsenn1=Vbase/gn, Vsenp1=Vbase/gp
Vbase: AK8996's quadratic function generator reference voltage (Vbase = 0.8V)
Find the coefficients (α ga, β ga, γ ga) as the secondary characteristics of the sensitivity temperature
drift of a sensor alone from the voltages for Vsenc1, Vsenn1 and Vsenp1.
2) From the AK8996's sensitivity temperature drift measurement result, find the gain values (gicc2, gicn2,
gicp2) which are compensated for by the quadratic function generator.
Depicted in this example is the AK8996's quadratic function sensitivity temperature drift
measurement result (same is also true with that of a linear function).
gicc2=Vicc2/Vicc2=1, gicn2=Vicn2/Vicc2, gicp2=Vicp2/Vicc2
For the gain values (gicc2, gicn2, gicp2) obtained, find the voltage which is output from the AK8996
quadratic function generator.
Vicc21=Vbase/gicc2, Vicn21=Vbase/gicn2, Vicp21=Vbase/gicp2
Vbase: AK8996's quadratic function generator reference voltage (Vbase = 0.8V)
Find the coefficients (a, b, c) as the secondary characteristics of the AK8996's sensitivity temperature
drift from the voltages for Vicc21, Vicn21 and Vicp21. In the same way, find the coefficients (d, e) as
the primary characteristics of the AK8996's sensitivity temperature drift from the voltages for Vicc11,
Vicn11 and Vicp11.
MS1055-E-02
35
2011/12