Melexis MLX90129 13.56MHz RFID传感和控制方案

Melexis公司的MLX90129是13.56MHz RFID传感器标签和数据采集器,它把外部电阻型传感器的精密采集链和各种接口组合在一起,能通过ISO15693 RFID前端或SPI端口进行接入和控制,仅需接上13.56MHz调谐天线,它就成为RFID温度计. MLX90129主要用于冷链监视,资产管理和监视,建筑物自动化,以及工业,医疗和住宅区控制与监视.本文介绍了MLX90129主要特性,方框图, RFID温度传感器标签, 数据采集器以及基于MCU的MLX90129应用电路, MLX90129评估板EVB90129主要特性,方框图,详细电路图和材料清单.

MLX90129: 13.56MHZ SENSOR TAG / DATALOGGER IC

The MLX90129 combines a precise acquisition chain for external resistive sensors, with a wide range of interface possibilities.

It can be accessed and controlled through its ISO15693 RFID front-end or via its SPI port.Without any other component than a 13,56MHz tuned antenna, it becomes a RFID thermometer. For measuring others physical quantities, one or two resistive sensors can be connected to make batteryless sensing point. Also, the chip can supply a regulated voltage to the other components of the application. Adding a battery will enable the use of the standalone data logging mode. The sensor output data is stored in the internal 3.5kbits user memory.

One can extend the storage capacity by connecting an external EEPROM to the SPI port.The SPI port can also connect the MLX90129 to a microcontroller which allows more specific applications, like adding actuating capability or RF transmission.

The MLX90129 has been optimized for low power, low voltage battery and battery-less applications.

MLX90129主要特性和优势:

Versatile A/D interface for resistive sensors

ISO-15693 13.56MHz transponder

Slave / Master SPI interface

4 k-bit EEPROM with access protection

Standalone data-logging mode

Ultra low power

Battery or battery-less applications

Low cost and compact design

MLX90129应用:

Cold chain monitoring

Asset management and monitoring (security and integrity)

Building automation

Industrial, medical and residential control and monitoring

图1.MLX90129功能方框图

图2.MLX90129方框图

The sensor signal conditioner is used to amplify, filter and convert the output voltage of resistive sensors. They may be an external single-ended or differential resistive sensor, or the internal temperature sensor. The two external sensors are supplied by a stable  reference voltage, provided by an integrated voltage regulator. The sensor output voltage is amplified thanks to a programmable-gain amplifier, and has its offset voltage compensated. Then, the conditioned sensor signal fits the input range of the A/D converter. The ADC converts the signal in a 16-bits code that can be stored or  transmitted.

The power management unit deals with the different power modes of the chip: it monitors the battery level, scavenges the energy coming from a RFID 13,56MHz field and makes the power-on reset signal. A regulator is used to supply the digital parts, but can also be used to supply some other external devices.

The Oscillators block contains different kind of oscillators: a very low power, low frequency 1kHz RC oscillator used as a wake-up timer, a low-power 32.768kHz quartz oscillator that can be used for an accurate time basis, and a high frequency 5MHz RC oscillator used for the digital controller.

The Register File contains all the configuration parameters of the chip. It may be loaded from the EEPROM after power-on, or as the result of a specific request from RFID or SPI.

The EE-Latches are used when device configuration parameters have to be immediately available.

The RFID front-end receives an external 13,56-MHz magnetic field, sensed on an external antenna coil. The antenna design is made easy thanks to an internal programmable high-Q capacitance (tuned during the test phase). From the antenna output voltage, it makes a stable clamped DC supply voltage, recovers the clock, and controls the modulation of the carrier and the demodulation of the incoming signal.

The EEPROM is a 4-kbits non-volatile memory, organized as 256 words of 16 bits divided in 39 reserved for configuration, 2 for default trimming value (EE-Latches #03,#04 and #09) backup and 215 available for the application (around 3.4 kbits user memory). Its access is protected by several security levels.

Some EE-Latches are also used when the stored data have to be immediately available for use.

The Digital Controller manages the accesses of the different interfaces (SPI, RFID) with the different memories (EEPROM, register file) and the sensor. It comprises the RFID ISO-15693 and SPI protocols, controls the sensor signal conditioner and stores or sends the ADC output code. It can also run some standalone applications, thanks to its unit called Direct Memory Access (DMA).

MLX90129应用案例:

图3.MLX90129 RFID温度传感器标签

图4.MLX90129 RFID多个传感器标签

图5.MLX90129数据采集器

图6.基于MCU的MLX90129应用电路

图7.串联电阻连接到外接传感器电路图

MLX90129评估板EVB90129

EVB90129  Evaluation Board for MLX90129 The EVB90129 is an assembled printed circuit board that simplifies evaluation of the MLX90129 sensor tag IC and to facilitate the development of wireless sensor applications based on the MLX90129.

The EVB90129 was developed to demonstrate a wide range of applications, from fully passive sensor tag operation to complex data logging. Each of its elements can be reconfigured by means of jumpers.

The board can be powered either by an external voltage supply, the on-board battery or the electromagnetic field from a RFID reader.

In addition to the internal temperature sensor of the MLX90129, the EVB90129 embeds 3 external sensors, light, temperature and potentiometer to demonstrate the flexibility for measurement of a variety of physical quantities. The custom prototyping area allows users to integrate their own sensor or circuit into this evaluation board.

The EVB90129 is capable of storing 128 Kbytes of datas in the SPI EEPROM memory connected to the MLX90129. The EVB90129 can be accessed and controlled through a contactless (RFID) or a contact (SPI) interface. The RFID access to the MLX90129 and the related commands are compliant with the ISO15693 standard. The SPI and other digital inputs/outputs from the MLX90129 are connected to an 8-pin connector of the EVB90129. This allows easy connection to a microcontroller.


图8.评估板EVB90129外形图

评估板EVB90129主要特性和优势:

_ Versatile A/D interface for resistive sensors

_ ISO-15693 13.56MHz transponder

_ Slave / Master SPI interface

_ 4 k-bit EEPROM with access protection

_ Standalone data-logging mode

_ Ultra low power

_ Battery or battery-less applications

_ Low cost and compact design

评估板EVB90129应用:

_ Asset management and monitoring (security and integrity)

_ Building automation

_ Supply chain monitoring of temperature and other parameters

_ Industrial, medical and residential control

图9.评估板EVB90129方框图

图10.评估板EVB90129电路图

评估板EVB90129材料清单(BOM):