CLRC663 Datasheet, PDF (121/132 Pages) NXP Semiconductors – Contactless reader IC

NXP Semiconductors
CLRC663
Contactless reader IC
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.
Remark: The layout has a major influence on the overall performance of the filter.
14.1.2 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 ISO/IEC 14443
communication scheme. Environmental influences have to be considered as well as
common EMC design rules.
For details refer to the NXP application notes.
14.1.3 Receiving circuit
The internal receiving concept of the CLRC663 makes use both side-bands of the
sub-carrier load modulation of the card response via a differential receiving concept (RXP,
RXN). No external filtering is required.
It is recommended to use the internally generated VMID potential as the input potential of
pin RX. This DC voltage level of VMID has to be coupled to the Rx-pins via R2 and R4. To
provide a stable DC reference voltage capacitances C4, C6 has to be connected between
VMID and ground. Refer to Figure 36
Considering the (AC) voltage limits at the Rx-pins the AC voltage divider of R1 + C3 and
R2 as well as R3 + C5 and R4 has to be designed. Depending on the antenna coil design
and the impedance matching the voltage at the antenna coil varies from antenna design to
antenna design. Therefore the recommended way to design the receiving circuit is to use
the given values for R1(= R3), R2 (= R4), and C3 (= C5) from the above mentioned
application note, and adjust the voltage at the RX-pins by varying R1(= R3) within the
given limits.
Remark: R2 and R4 are AC-wise connected to ground (via C4 and C6).
CLRC663
Product data sheet
COMPANY PUBLIC
All information provided in this document is subject to legal disclaimers.
Rev. 3.3 — 3 April 2012
171133
© NXP B.V. 2012. All rights reserved.
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