CLRC632 Datasheet, PDF (140/163 Pages) NXP Semiconductors – Multiple Protocol Contactless Reader IC

Philips Semiconductors
Product Specification Rev. 3.0; May 2003
Multiple Protocol Contactless Reader IC
CL RC632
20.2 Circuit Description
The matching circuit consists of an EMC low pass filter (L0 and C0), a matching circuitry (C1 and C2), and a
receiving circuit (R1, R2, C3 and C4), and the antenna itself.
For more detailed information about designing and tuning an antenna please refer to the Application Note
’MIFARE^ and I CODE MICORE reader IC family; Directly Matched Antenna Design’ and
‘MIFARE^ (14443A) 13,56 MHz RFID Proximity Antennas’.
20.2.1 EMC LOW PASS FILTER
The MIFARE^ system operates at a frequency of 13.56 MHz. This frequency is generated by a quartz
oscillator to clock the CL RC632 and is also the basis for driving the antenna with the 13.56 MHz energy
carrier. This will not only cause emitted power at 13.56 MHz but will also emit power at higher harmonics.
The international EMC regulations define the amplitude of the emitted power in a broad frequency range.
Thus, an appropriate filtering of the output signal is necessary to fulfil these regulations.
A multi-layer board it is recommended to implement a low pass filter as shown in the circuit above. The low
pass filter consists of the components L0 and C0. The recommended values are given in the above
mentioned application notes.
Note: To achieve best performance all components shall have at least the quality of the recommended ones.
Note: The layout has a major influence on the overall performance of the filter.
20.2.2 ANTENNA MATCHING
Due to the impedance transformation of the given low pass filter, the antenna coil has to be matched to a
certain impedance. The matching elements C1 and C2 can be estimated and have to be fine tuned
depending on the design of the antenna coil.
The correct impedance matching is important to provide the optimum performance. The overall Quality factor
has to be considered to guarantee a proper ISO14443 communication scheme. Environmental influences
have to considered as well as common EMC design rules.
For details refer to the above mentioned application notes.
Note: Do not exceed the current limits I_TVDD, otherwise the chip might be destroyed.
Note: The overall 13.56MHz RFID proximity antenna design with the CL RC632 chip is straight forward and
doesn’t require a special RF-know how. However, all relevant parameters have to be considered to
guarantee an overall optimum performance together with international EMC compliance.
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