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Application note
COMPANY PUBLIC
Rev. 1.1 — 19 June 2018
345311
Typically, the NFC antenna design uses higher target impedances even in reader mode
(RM), since the required operating volume is much smaller and at the same time the
current consumption must be as low as possible. For impedances higher than 50Ω it
might be better to target a “parallel” resonance as shown in Fig 36b.
a. “Serial” resonance (low impedance)
b. “Parallel “resonance (high impedance)
Fig 36. RM Antenna matching with low and high impedance
4.3.1 Antenna tuning for RM and CM
The antenna tuning supporting both reader mode (RM) and card mode (CM) needs to
consider the ANT1 and ANT2 pins of the PN5180. In CM these pins are in “high Z” state,
in RM the ANBT1 and ANT2 are low.
The Fig 37 shows the simulation of the NFC antenna in RM. The ANT1 / ANT2
connection is simulated and measured with a 10Ω resistor.
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