MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
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 (Tomin and Tomax) and one for
Ta (Tarange: the 8MSB are foreseen for Tamax and the 8LSB for Tamin).
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 2.56 °C.
The object data for PWM is rescaled according to the following equation:
TRAM −T
T
−T
MINEEPROM
MAXEEPROM
MINEEPROM
TPWM
=
, KPWM
=
obj
obj
KPWM
1023
obj
The TRAM is the linearized Tobj, 16-bit (0000…FFFFh, 0000 for -273.15°C and FFFFh for +382.2°C) and the
result is a 10-bit word, in which 000h corresponds to ToMIN[°C], 3FFh corresponds to ToMAX[°C] and 1LSB
ToMAX −ToMIN
corresponds to
[°C]
1023
TMIN
= TMIN ∗100 LSB
EEPORM
TMAX
= TMAX ∗100LSB
EEPORM
The ambient data for PWM is rescaled according to the following equation:
TRAM −T
T
−T
MINEEPROM
MAXEEPROM
MINEEPROM
TPWM
=
, KPWM
=
ambient
ambient
KPWM
1023
ambient
The result is a 10-bit word, where 000h corresponds to -38.2 °C (lowest Ta that can be read via PWM), 3FFh
TMAX −TMIN
corresponds to 125 °C (highest Ta that can be read via PWM) and 1LSB corresponds to
[°C]
1023
100
TMIN
=
[
TMIN
−
(
− 38.2
)]
∗
LSB
EEPORM
64
100
TMAX
=
[
TMAX
−
(
− 38.2
)]
∗
LSB
EEPORM
64
3901090614
Rev 003
Page 20 of 40
Data Sheet
03/Oct/2007
MELEXIS [ Melexis Microelectronic Systems ]
