MLX75030 Datasheet, PDF (23/72 Pages) Melexis Microelectronic Systems – Universal ActiveLight Sensor Interface

MLX75030 Universal ActiveLight Sensor Interface
Datasheet
• I_x:
• ambout_x:
• TC_Iref:
• O_x:
• α_x, β_x:
calculated input light value
16-bit ADC converted value of the ambient channel
temperature coefficient of the reference current (typ. Value = +375ppm/K)
offset of the measurement (digital value)
calibration values for channel x (see below)
During calibration at least 2 light levels (I_x1 and I_x2) have to be supplied to the target ambient channel (x) with its photodiode
at the same known temperature T. The closer these values are chosen to the range used in application, the more accurate
the final result will be. During the setting of these light levels, the output of ambient channel x: ambout_x1 and ambout_x2 are
measured. This results in 2 equations and 2 unknowns: α_x and β_x. Both unknowns can be calculated from following formulas:
α=
T
ln_{}
I₁
I₂

ambout₁ − ambout₂
and
β
=
ln

I₁
1


−
α

ambout₁
T
− 2¹⁵

(2)
Note that these 2 values automatically correct any gain error of the connected photodiode and used lens system.
REVISION 005 – DECEMBER 2013
3901075030
PAGE 23 OF 72