MLX90614 family Single and Dual Zone Infra Red Thermometer in TO-39 1. Functional diagram2. General Description The MLX90614 is an Infra Red thermometer for non- M LX90614Axx : Vdd=4.5...5.5V contact temperature measurements. Both the IR J1 1 MLX90614 SCL U1 sensitive thermopile detector chip and the signal SCL Vz conditioning ASSP are integrated in the same TO-39 can. P W M 4 SDA Vss SDA 2 Thanks to its low noise amplifier, 17-bit ADC and Vdd Vdd powerful DSP unit, a high accuracy and resolution of the C1 3 thermometer is achieved. GND CON1 0.1uF The thermometer comes factory calibrated with a digital C1 value and type may differ PWM and SMBus (System Management Bus) output. in different applications for optimum EMC As a standard, the 10-bit PWM is configured to continuously transmit the measured temperature in M LX9 0614 connection to SM Bus range of -20…120˚C, with an output resolution of 0.14˚C. Figure 1: Typical application schematics The factory default POR setting is SMBus. 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°C…125°C for the ambient temperature and -70°C…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°C…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. REVISION 13 - SEPTEMBER 23, 2019 3901090614
