How does MLX90129 work as a transponder chip or RFID tag? It does not even have its own antenna. We can actually fabricate our own RFID tag simply just having an antenna along with a capacitor. Then what is the distinctive feature does MLX90129 offer as a transponder?
How does it work when there are sensors hooked up with it? Does it change the resonance frequency according to the measurement of the resistive sensors? (But according to the datasheet it only works at 13.56 MHz.). If its not the resonance frequency then what is the parameter it echoes back from the sensor measurement?
Thanks in advance.
MLX90129 is a kind of EEPROM memory that could communicate via two interfaces - SPI and ISO15693 RFID protocols. To the proper function it needs connection of external planar coil antenna tuned to the internal capacitance (typical 75 pF). One could also try EVB90129 evaluation board ready to use as an RFID sensing platform (transponder with sensing capabilities)
The main distinctive feature that MLX90129 offers is the possibility to direct connection of any resistive sensor to it and then performing of wireless data transfer - it needs no battery, unless you want to use it as a data logger.
This chip transfers a data in digitized form via the typical ISO 15693 protocol, which allows transfer of memory stored data from RFID chip to the reader - not only UID data. Therefore, the chip is equipped in ADC unit and after some signal codnitioning (amplification) the analog signal from connected sensor changes form to the digitized one and it is stored in EEPROM or transfer wirelessely to the reader immediately.
There are also RFID chips on the market presenting similar capabilities, for instance M24LR64E from ST Microelectronics.
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