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2017-09-09 10:09  
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Manufactured by ATMEL, the U2270B IC forms the RF front end of a
Read/Write RFID base station. Used in 125kHz  RFID systems it can be
used in such applications as access control, immobilizer systems,
process control and general Contactless ID systems.

The U2270B features:·
·Energy transfer circuits to supply the transponder.
·On chip power supply regulation.
·Tunable oscillator and coil driver.
·Signal processing circuits that allow easy microcontroller interface.

You can buy U2270B IC's direct from our online shopfront.

The U2207B has various operating modes. In this example a 12V supply allows for greater reading range.

The U2270B has an on board rectifier which simplifies the generation of a external supply  for a digital processor (Vext ~ 4.6-6.3V).

Once the circuit parameters L and Cres are derived the frequency of the on chip oscillator can be set. The U2207B has an on chip oscillator which drives the antenna coil. This frequency is selected by a fixed resistor between the pins Vs, and RF.  In the example above this resistance is the sum of R1 and R2, giving us a resistance value of 110 ohms.

In operation the antenna coil generates an electromagnetic field at 125kHz. When a Transponder enters this field it draws power from it, and when sufficient power is available it starts to transmit its data by modulating the RF field.  The modulated field is sensed by the U2270B at the INPUT pin. The raw demodulated data generated by the action of the transponder is then made available at the OUTPUT pin for the digital processor to decode.  The demodulated data appearing at the OUTPUT pin can be encoded in various protocols depending on the type of RFID transponder that is being used. For a description of Read Only transponders utilizing EM4100 protocol see EM100 protocol.

In addition to the OUTPUT pin the digital processor can control the CFE input pin of the U2270B to allow data transfer from reader to transponder. When CFE is set low the RF field is turned off. By turning the RF field on and off in a predefined manner data can be sent to the transponder. This is required when writing data to a transponder capable of READ/WRITE or cryptographic functionality.