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Application Note

Antenna Design for MLX90130/32

13.56MHz RFID / NFC Transceivers Family

390119013201 Page 1 of 11 May 12

Rev 001

Scope

The objective of this application note is to provide guidelines to calculate the external matching network to

adapt the driver’s outputs of the MLX90132 NFC transceiver IC and MLX90130, RFID Transceiver IC to

the inductive impedance coil used as an antenna. This to achieve best RF performances communicating

with memory TAGs compliant with ISO/IEC14443, ISO/IEC15693 and ISO/IEC18092 RFID standards

(MLX90132).

Applications

 RFID / NFC General Purpose

Related Melexis Products

Part No.

Temperature suffix

Package Code

Option code

MLX90130xxx

MLX90132xxx

E (-40°C to 105°C)

LQ [Lead free QFN 5x5 32 leads]

Introduction

The MLX90130/32 serie is a 13.56MHz RFID /

NFC transceiver ICs family. It has been designed

to support communications with RF memory

transponders compliant with ISO/IEC14443,

ISO/IEC15693 and ISO/IEC18092 (MLX90132)

RFID standards.

To allow communication with RF memory

transponders the MLX90130/32 has to be

connected to a suitable inductive antenna load,

most of the time simply composed of a

square/circle shape loop directly printed on a PCB.

Three external capacitors will be used to match the

dual driver architecture of the MLX90130 /

MLX90132 to the inductive loop antenna and also

to insure proper resonance at 13.56MHz.

The reception of transponder message is made

using two external resistors connected on both

RX1 and RX2 pin of the MLX90130/32. Those

resistor values as well as the internal equivalent

impedance of the reception chain have also to be

taken into account into the calculation of the

matching network.

Finally, there is also a possibility to add an EMI

filter to reduce as much as possible the emissions

of higher harmonics of the 13.56MHz transmitted

signal. This EMI filters would not change the

matching network components and would be

simply composed of a LC filter directly connected

at the two driver outputs.

Application Note

Antenna Design Guidelines for MLX90130 / MLX90132

13.56MHz RFID / NFC Transceivers Family

390119013201 Page 2 of 11 May 2012

Rev 002

Contents

Scope ............................................................................................................................................................ 1

1 Output impedance of the MLX90130 / MLX90132 ............................................................................... 3

2 Inductive antenna impedance ............................................................................................................... 3

3 Need for impedance matching .............................................................................................................. 4

4 Impedance matching circuit .................................................................................................................. 4

4.1 Antenna circuit description ............................................................................................................... 4

4.2 Antenna circuit simplifications .......................................................................................................... 5

5 Numerical example (DVK90132) .......................................................................................................... 6

6 Conclusion ............................................................................................................................................ 7

7 Appendix A: detail of calculation ........................................................................................................... 8

7.1 Demonstration of C11 and C22 calculation ...................................................................................... 8

7.2 Antenna parallel equivalent model ................................................................................................. 10