EVB90615 Datasheet, PDF (18/30 Pages) Melexis Microelectronic Systems – Infra Red Thermometer

MLX90615
Infra Red Thermometer
8.6.2 Customizing the temperature range for PWM output
The calculated ambient and object temperatures are stored in RAM with a resolution of 0.02 °C (15 bit). The
PWM operates with a 10-bit number so the transmitted temperature is rescaled in order to fit in the desired
range.
For this goal 2 cells in EEPROM are foreseen to store the desired temperature range, PWM T min and PWM
T range.
Thus the output range can be programmed with an accuracy of 0.02 °C.
The data for PWM is rescaled according to the following equation:
T = ^T _K^{− T} , K _PWM
RAM
MIN_EEPROM
PWM
PWM
= ^TRANGEEEPROM
1023
The T_RAM is the linearized temperature, 15-bit (2D8A…4BD0h, 2D8A for -40°C and 4BD0h for +115°C) and
the result is a 10-bit word, in which 000h corresponds to PWM T_MIN[°C], 3FFh corresponds to PWM T_MAX[°C]
and 1LSB corresponds to
T_MAX − To_MIN
1023
[°C] , (T_{MAX =} T_{MIN +} T_RANGE)
T_{MIN EEPORM} = T_MIN ∗ 50 LSB
T_{MAX EEPORM} = T_MAX ∗ 50 LSB
3901090615
Rev 001
Page 18 of 30
Data Sheet
28/Aug/2008