Data Sheet
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 (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 2.56 °C.
The object data for PWM is rescaled according to the following equation:
1023
,
EEPROMEEPROMEEPROM
obj
MINMAX
obj
PWM
obj
PWM
MINRAM
PWM
TT
K
K
TT
T
−
=
−
=
The T
RAM
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 To
MIN
[°C], 3FFh corresponds to To
MAX
[°C] and 1LSB
corresponds to
1023
MINMAX
ToTo −
[°C]
100∗=
MINMIN
TT
EEPORM
LSB
100∗=
MAXMAX
TT
EEPORM
LSB
The ambient data for PWM is rescaled according to the following equation:
1023
,
EEPROMEEPROM
ambient
EEPROM
ambient
MINMAX
ambient
PWM
PWM
MINRAM
PWM
TT
K
K
TT
T
−
=
−
=
The result is a 10-bit word, where 000h corresponds to -38.2 °C (lowest Ta that can be read via PWM), 3FFh
corresponds to 125 °C (highest Ta that can be read via PWM) and 1LSB corresponds to
1023
MINMAX
TT −
[°C]
()
[]
64
100
2.38 ∗−−=
MINMIN
TT
EEPORM
LSB
()
[]
64
100
2.38 ∗−−=
MAXMAX
TT
EEPORM
LSB
3901090614 Page 22 of 42 Data Sheet
Rev 004 30/Jul2008