MLX90614_15 Datasheet, PDF (2/51 Pages) Melexis Microelectronic Systems – Single and Dual Zone Infra Red Thermometer in TO-39

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
General description (continued)
The MLX90614 is built from 2 chips developed and manufactured by Melexis:
• The Infra Red thermopile detector MLX81101
• The signal conditioning ASSP MLX90302, specially designed to process the output of IR sensor.
The device is available in an industry standard TO-39 package.
Thanks to the low noise amplifier, high resolution 17-bit ADC and powerful DSP unit of MLX90302 high
accuracy and resolution of the thermometer is achieved. The calculated object and ambient temperatures are
available in RAM of MLX90302 with resolution of 0.01˚C. They are accessible by 2 wire serial SMBus
compatible protocol (0.02°C resolution) or via 10-bit PWM (Pulse Width Modulated) output of the device.
The MLX90614 is factory calibrated in wide temperature ranges: -40…125˚C for the ambient
temperature and -70…380˚C for the object temperature.
The measured value is the average temperature of all objects in the Field Of View of the sensor. The
MLX90614 offers a standard accuracy of ±0.5˚C around room temperatures. A special version for medical
applications exists offering an accuracy of ±0.2˚C in a limited temperature range around the human body
temperature.
It is very important for the application designer to understand that these accuracies are only guaranteed
and achievable when the sensor is in thermal equilibrium and under isothermal conditions (there are no
temperature differences across the sensor package). The accuracy of the thermometer can be influenced by
temperature differences in the package induced by causes like (among others): Hot electronics behind the
sensor, heaters/coolers behind or beside the sensor or by a hot/cold object very close to the sensor that not
only heats the sensing element in the thermometer but also the thermometer package.
This effect is especially relevant for thermometers with a small FOV like the xxC and xxF as the energy
received by the sensor from the object is reduced. Therefore, Melexis has introduced the xCx version of the
MLX90614. In these MLX90614xCx, the thermal gradients are measured internally and the measured
temperature is compensated for them. In this way, the xCx version of the MLX90614 is much less sensitive to
thermal gradients, but the effect is not totally eliminated. It is therefore important to avoid the causes of thermal
gradients as much as possible or to shield the sensor from them.
As a standard, the MLX90614 is calibrated for an object emissivity of 1. It can be easily customized by
the customer for any other emissivity in the range 0.1…1.0 without the need of recalibration with a black body.
The 10-bit PWM is as a standard configured to transmit continuously the measured object temperature
for an object temperature range of -20…120˚C with an output resolution of 0.14˚C. The PWM can be easily
customized for virtually any range desired by the customer by changing the content of 2 EEPROM cells. This
has no effect on the factory calibration of the device.
The PWM pin can also be configured to act as a thermal relay (input is To), thus allowing for an easy
and cost effective implementation in thermostats or temperature (freezing / boiling) alert applications. The
temperature threshold is user programmable. In a SMBus system this feature can act as a processor interrupt
that can trigger reading all slaves on the bus and to determine the precise condition.
The thermometer is available in 2 supply voltage options: 5V compatible or 3V (battery) compatible.
The 5V can be easily adopted to operate from a higher supply voltage (8…16V, for example) by use of few
external components (refer to “Applications information” section for details).
An optical filter (long-wave pass) that cuts off the visible and near infra-red radiant flux is integrated in
the package to provide ambient and sunlight immunity. The wavelength pass band of this optical filter is from
5.5 till 14µm (except for xCH and xCI type of devices which incorporate uncoated silicon lens).
3901090614
Rev 009
Page 2 of 52
Data Sheet
June 29, 2015