EVB90614 Datasheet, PDF (24/52 Pages) Melexis Microelectronic Systems – Single and Dual Zone Infra Red Thermometer in TO-39

Example: (see Figure 17 above):
Configuration:
Sensor1 = Ta, Sensor2 = T_obj1 Config Reg[5:4] = 00b,
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
T_{A _ MIN}
T_{A _ MAX}
0C
T_{A _ RANGE _ L} EEPROM
100 ^{TA _ min 38.2}
64
59.6875 60d 0x3C
60 C
T_{A _ RANGE _ H} EEPROM
100 ^{TA _ max 38.2}
64
153.4375 153d 0x99
T_{A _ RANGE} EEPROM ,0x03 T : T _{A_ RANGE _ H A _ RANGE _ L} 0x993C
T_{O _ MIN} 0 C T_{O _ MIN} EEPROM ,0x01 100 T_{O _ min} 273.15 27315d 0x6 AB3
T_{O _ MAX} 50 C T_{O _ MAX} EEPROM ,0x00 100 T_{O _ min} 273.15 32315d 0x7E3B
Captured high durations are:
Sensor 1 – t = 16.875ms at period T = 100ms thus the duty cycle is Duty_S1
16.875
100
0.16875
Sensor 2 – t = 73.125ms at period T = 100ms thus the duty cycle is Duty_{S 2}
The temperatures are calculated as follows:
73.125
100
0.73125
T_A 4 Duty_S1 Start1
T T _{A_ MAX}
A _ MIN
T_{A _ MIN}
T_A 4 0.16875 0.0625 60 0 0 25.5 C
T_O1 4
Duty_S2 Start2
T T _{O _ MAX}
O _ MIN
T_{O _ MIN}
T_O1 4 0.73125 0.5625 50 0 0 33.75 C
8.5.3 Customizing the temperature range for PWM output
The calculated ambient and object temperatures are stored in RAM with a resolution of 0.01°C (16 bit).
The PWM operates with a 10-bit word 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 range for To (To_min and To_max) and
one for Ta (Ta_range: the 8MSB are foreseen for Ta_max and the 8LSB for Ta_min).
Thus the output range for To can be programmed with an accuracy of 0.01°C, while the corresponding Ta range
can be programmed with an accuracy of 0.64°C.
The object data for PWM is rescaled according to the following equation:
T_{PWM obj}
T T _RAM
MIN _EEPROM
K ^{, K} _{PWM obj}
PWM obj
T_{MAX EEPROM}
T_{MIN EEPROM}
1023
3901090614
Rev 008
Page 24 of 52
Data Sheet
February 28, 2013