mfrc531 NXP Semiconductors, mfrc531 Datasheet - Page 99

• Manufacturer Part Number: mfrc531
• Description: Iso/iec 14443 Reader Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
MFRC531_34
Product data sheet
PUBLIC
15.1.2.1 EMC low-pass filter
15.1.2.2 Antenna matching
15.1.2 Circuit description
The matching circuit consists of an EMC low-pass filter (L0 and C0), matching circuitry
(C1 and C2n), a receiver circuit (R1, R2, C3 and C4) and the antenna itself.
Refer to the following application notes for more detailed information about designing and
tuning an antenna.
The MIFARE system operates at a frequency of 13.56 MHz. This frequency is generated
by a quartz oscillator to clock the MFRC531. It is also the basis for driving the antenna
using the 13.56 MHz energy carrier. This not only causes power emissions at 13.56 MHz,
it also emits power at higher harmonics. International EMC regulations define the
amplitude of the emitted power over a broad frequency range. To meet these regulations,
appropriate filtering of the output signal is required.
A multilayer board is recommended to implement a low-pass filter as shown in
The low-pass filter consists of the components L0 and C0. The recommended values are
given in Application notes MICORE reader IC family; Directly Matched Antenna Design
Ref. 1
Remark: To achieve best performance, all components must be at least equal in quality to
those recommended.
Remark: The layout has a major influence on the overall performance of the filter.
Due to the impedance transformation of the low-pass filter, the antenna coil has to be
matched to a given impedance. The matching elements C1 and C2n can be estimated
and have to be fine tuned depending on the design of the antenna coil.
The correct impedance matching is important to ensure optimum performance. The
overall quality factor has to be considered to guarantee a proper ISO/IEC 14443 A and
ISO/IEC 14443 B communication schemes. Environmental influences have to considered
and common EMC design rules.
Refer to Application notes MICORE reader IC family; Directly Matched Antenna Design
Ref. 1
Remark: Do not exceed the current limits (I
destroyed.
Remark: The overall 13.56 MHz RFID proximity antenna design in combination with the
MFRC531 IC does not require any specialist RF knowledge. However, all relevant
parameters have to be considered to guarantee optimum performance and international
EMC compliance.
•
•
MICORE reader IC family; Directly Matched Antenna Design
MIFARE (14443 A) 13.56 MHz RFID Proximity Antennas
and MIFARE (14443 A) 13.56 MHz RFID Proximity Antennas
and MIFARE (14443 A) 13.56 MHz RFID Proximity Antennas
Rev. 3.4 — 26 January 2010
056634
DD(TVDD)
), otherwise the chip might be
Ref.
ISO/IEC 14443 reader IC
Ref. 1
2.
Ref.
Ref. 2
MFRC531
© NXP B.V. 2010. All rights reserved.
2.
for details.
Figure
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