CLRC663 datasheet(124/177 Pages) NXP

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NXP Semiconductors

CLRC663

High performance multi-protocol NFC frontend CLRC663 and CLRC663 plus

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 subcarrier load modulation of

the card response via a differential receiving concept (RXP, RXN). No external filtering is required.

It is recommended using 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).

14.1.4 Antenna coil

The precise calculation of the antenna coils’ inductance is not practicable but the inductance can be

estimated

using the following formula. We recommend designing an antenna either with a circular or rectangular shape.

(4)

• I1 - Length in cm of one turn of the conductor loop

• D1 - Diameter of the wire or width of the PCB conductor respectively

• K - Antenna shape factor (K = 1.07 for circular antennas and K = 1.47 for square antennas)

• L1 - Inductance in nH

• N1 - Number of turns

• Ln: Natural logarithm function

The actual values of the

antenna inductance, resistance, and capacitance at 13.56 MHz depend on various

parameters such as:

• antenna construction (Type of PCB)

• thickness of conductor

• distance between the windings

• shielding layer

• metal or ferrite in the near environment

Therefore a measurement of those parameters under real life conditions, or at least a rough measurement and

a tuning procedure are highly recommended to guarantee a reasonable performance. For details, refer to the

above mentioned application notes.

CLRC663

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 5.3 — 3 January 2024

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