MLX90251
Programmable Linear Hall Effect Sensor
3901090251 Page 10 of 20 Data Sheet
Rev 012 Oct/2012
The MLX90251 also has an additional stage, Fine Gain, for fine tuning the Sensitivity. The stage (parameter
FG) follows the RG and provides a 10 bit adjustment. The small signal gain of the FG is within 1.0 and 2.5.
The RG and FG parameters are adjusted in the application to calibrate the device's sensitivity (gain) and
output slope transfer characteristic. The function for the fine gain is given in the following equation:
1023
*6.01
1
FG
GainFine
−
=
Note. The one bit parameter INVERT is used to fix the “sign” of the sensitivity. A value of 0 makes the
Sensitivity positive and the output voltage increases in response to a South magnetic field. A value of 1
makes the Sensitivity negative and the output voltage decreases in response to a South magnetic field.
Refer to section 10.5, Sensitivity Polarity, for more information on INVERT.
10.4 Sensitivity Range Selection
Each unit is characterized over temperature during final test to optimize its performance and accuracy. To
achieve the best possible Sensitivity Temperature Compensation, TempCo, each unit is optimized for use
within a specific Sensitivity range. This is represented in the ordering information by the option code. There
are four available ranges, option codes 0, 1, 2 and 3. The option code corresponds with the two MSB of the
RG parameter. Each device is tested to meet the TempCo specification in the Sensitivity range determined
by the RG parameter (RG = 0...3, RG = 4…7, RG = 8…11 or RG = 12…15), regardless of the FG parameter.
Option Code Rough Gain Sensitivity Range
(mV/mT)
Typical Magnetic Field Range
(mT, B
- B
)
xxx-000 0-3 (00 xx) 2.6 < S < 15 333 < B < 800
xxx-100 4-7 (01 xx) 10 < S < 35 156 < B < 333
xxx-200 8-11 (10 xx) 18 < S < 90 62 < B < 156
xxx-300 12-15 (11 xx) 50 < S < 210 6 < B < 62
Table 9: Optimized Sensitivity Range
The next figures show the typical Sensitivity versus the FG and RG parameters. The gray areas are
representative of the chip to chip dispersion (i.e.: for the same RG and FG parameters, the Sensitivity can
vary from chip to chip). There is a large overlap between the different ranges for use of one range for
applications with large magnetic and/or mechanical dispersions. The Sensitivity graphs and tables can be
used to select the right device type for the application. If one is unsure of the applications magnetic design
and the desired Sensitivity range Melexis recommends option code 2.
