Melexis 公司的MLX90614是用来非接触测量的红外温度传感器。在TO-39封装中集成了红外温度检测芯片和信号调理ASIC，包括低噪音放大器，17位ADC和功能强大的DSP单元，使温度计能达到高精度和高分辨率。MLX90614测量的温度范围从-70 到380 °C，精度为0.5°C，有着广泛的应用。本文介绍MLX90614的主要性能，工作原理，应用领域以及多种应用电路图和MLX90614评估板的详细电路图。
MLX90614 Digital, plug & play, infrared thermometer in a TO-can 
图1。MLX90614外形图
The MLX90614 is an Infra Red thermometer for non contact temperature measurements. Both the IR sensitive thermopile detector chip and the signal conditioning ASIC are integrated in the same TO-39 can.
Integrated into the MLX90614 are a low noise amplifier, 17-bit ADC and powerful DSP unit thus achieving high accuracy and resolution of the thermometer.
The thermometer comes factory calibrated with a digital SMBus output giving full access to the measured temperature in the complete temperature range(s) with a resolution of 0.02°C.
The user can configure the digital output to be PWM. As a standard, the 10-bit PWM is configured to continuously transmit the measured temperature in range of -20 to 120 °C, with an output resolution of 0.14 °C.
The MLX90614 is a ready-to use low-cost non contact thermometer provided from Melexis with output data linearly dependent on the object temperature with high accuracy and extended resolution.
It supports versatile customization to a very wide range of temperatures, power supplies and refresh rates.
The user can program the internal object emissivity correction for objects with a low emissivity. An embedded error checking and correction mechanism provides high memory reliability.
The sensors are housed in an industry standard TO39 package for both single- and dual-zone IR thermometers. The thermometer is available in automotive grade and can use two different packages for wider applications’ coverage.
The low power consumption and sleep mode make the thermometer ideally suited for handheld mobile applications.
The digital sensor interface can be either a power-up-and-measure PWM or an enhanced access SMBus compatible protocol. Systems with more than 100 devices can be built with only two signal lines. Dual zone non contact temperature measurements are available via a single line (extended PWM).
A built-in thermal relay function further extends the easy implementation of wide variety of freezing/boiling prevention and alert systems, as well as thermostats (no MCU is needed).
工作原理：
The operation of the MLX90614 is controlled by an internal state machine, which controls the measurements and calculations of the object and ambient temperatures and does the post-processing of the temperatures to output them through the PWM output or the SMBus compatible interface.
The ASSP supports 2 IR sensors (second one not implemented in the MLX90614xAx).The output of the IR sensors is amplified by a low noise low offset chopper amplifier with programmable gain, converted by a Sigma Delta modulator to a single bit stream and fed to a powerful DSP for further processing. The signal is treated by programmable (by means of EEPROM contend) FIR and IIR low pass filters for further reduction of the band width of the input signal to achieve the desired noise performance and refresh rate. The output of the IIR filter is the measurement result and is available in the internal RAM. 3 different cells are available: One for the on-board temperature sensor (on chip PTAT or PTC) and 2 for the IR sensors.
Based on results of the above measurements, the corresponding ambient temperature Ta and object temperatures To are calculated. Both calculated temperatures have a resolution of 0.01 °C. The data for Ta and To can be read in two ways: Reading RAM cells dedicated for this purpose via the 2-wire interface (0.02°C resolution, fixed ranges), or through the PWM digital output (10 bit resolution, configurable range).
In the last step of the measurement cycle, the measured Ta and To are rescaled to the desired output resolution of the PWM) and the recalculated data is loaded in the registers of the PWM state machine, which creates a constant frequency with a duty cycle representing the measured data. 
图2。MLX90614方框图
MLX90614主要特性和优势：
Small size, low cost
Easy to integrate
Factory calibrated in wide temperature range: -40 to 125 °C for sensor temperature and -70 to 380 °C for object temperature.
High accuracy of 0.5°C over wide temperature range (0..+50 C for both Ta and To)
Medical accuracy of 0.1°C in a limited temperature range available on request
Measurement resolution of 0.01°C
Single and dual zone versions
SMBus compatible digital interface for fast temperature readings and building sensor networks
Customizable PWM output for continuous reading
Available in 3V and 5V versions
Simple adaptation for 8 to 16V applications
Power saving mode
Different package options for applications and measurements versatility
Automotive grade
应用案例：
High precision non-contact temperature measurements;
Thermal Comfort sensor for Mobile Air Conditioning control system;
Temperature sensing element for residential, commercial and industrial building air conditioning;
Windshield defogging;
Automotive blind angle detection;
Industrial temperature control of moving parts;
Temperature control in printers and copiers;
Home appliances with temperature control;
Healthcare;
Livestock monitoring;
Movement detection;
Multiple zone temperature control – up to 100 sensors can be read via common 2 wires
Thermal relay/alert
Body temperature measurement
应用案例介绍：
1．SMBus 配置中MLX90614 温度计的使用 
图3。MLX90614 SMBus 连接图
Connection of the MLX90614 to SMBus with 3.3V power supply. The MLX90614 has diode clamps SDA/SCL to Vdd so it is necessary to provide MLX90614 with power in order not to load the SMBus lines.
2．SMBus 配置中多个MLX90614 的应用 
图4。SMBus 网络中多个MLX90614 应用电路图
The MLX90614 supports a 7-bit slave address in EEPROM, thus allowing up to 127 devices to be read via two common wires. With the MLX90614BBx this results in 254 object temperatures measured remotely and an additional 127 ambient temperatures which are also available. Current source pull-ups may be preferred with higher capacitive loading on the bus (C3 and C4 represent the lines’ parasitics), while simple resistive pull-ups provide the obvious low cost advantage.
3． PWM 输出应用
The PWM mode is free-running after POR when configured in EEPROM. The SCL pin must be forced high (can be shorted to Vdd pin) for PWM mode operation.
A pull-up resistor can be used to preserve the option for SMBus operation while having PWM as a default as is shown on Figure 25.
