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U3280M_07 Datasheet, PDF (14/21 Pages) ATMEL Corporation – Transponder Interface for Microcontroller
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The antenna coil must be connected with a capacitor as a parallel LC resonant circuit to the Coil
1 and Coil 2 pins of the IC. The resonance frequency f0 of the antenna circuit should be in the
range of 100 kHz to 150 kHz.
The correct LC combination can be calculated with the following formula:
LA
=
-----------------------1------------------------
CA × (2 × π × f0)2
Figure 5-1. Antenna Circuit Connection
Coil 1
LA
CA
Coil 2
Example: Antenna frequency: f0 = 125 kHz, capacitor: CA = 2.2 nF
LA
=
------------------------------------1--------------------------------------
2.2 nF × (2 × π × 125 kHz)2
=
737 µH
14 U3280M
4688D–RFID–03/07
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