MLX90288 Datasheet, PDF (13/19 Pages) Melexis Microelectronic Systems – SMD Programmable Linear Hall Sensor IC Featuring Analog Ratiometric Output

MLX90288
SMD Programmable Linear Hall Sensor IC
Featuring Analog Ratiometric Output
7 Thermal Sensitivity Drift Compensation
7.1 Introduction
The embedded temperature sensor is digitized via the main path ADC before each analog amplified Hall
sensor voltage ADC in case TEMPSENSOR is enabled. This temperature information is used to generate
either an address for a ROM Look-up Table in order to obtain a quadratic temperature compensation
(SECONDORDERTC=1), or a value proportional to the temperature that allows a linear IC gain
compensation (SECONDORDERTC=0). Both compensations rely on the TEMPOFF and TEMPTC
parameters.
7.2 Linear Compensation (1^st Order)
The conventional linear temperature compensation proves to be adequate for small application temperature
ranges and/or small magnet temperature coefficients. In such cases the error induced by the linear approach
are limited and prove to be good enough for the desired system sensitivity drift.
7.3 Quadratic Compensation (2^nd Order)
This look up table is stored in ROM and contains the inverse transfer function of a specific magnetic flux
density over temperature. It should be used for magnets with temperature coefficients lower than -1500
ppm/degC, as is typically the case for plastic bonded magnets. Such magnet temperature coefficients can not
optimally be compensated by the linear method (see Application Note “Temperature Compensation for Linear
Programmable Hall effect sensors” on the Melexis webpage). By multiplying the output of the ROM table with
the amplified magnetic flux density signal in the digital domain, the magnet temperature drift is compensated
for, resulting in a (nearly) temperature independent sensitivity of the whole system (magnet + IC).
Gain compensation
-50.00
-30.00
1.3
1.25
1.2
1.15
1.1
1.05
1
0.95
0.9
0.85
-10.00 10.00
30.00
50.00
70.00
90.00
110.00 130.00 150.00
Temperature [Degree]
Figure 3: ROM table - 2^nd order gain compensation
3901090288
Rev 002
Page 13 of 19
May/12