NXP Semiconductors
AN11740
PN5180 Antenna design
AN11740
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Application note
COMPANY PUBLIC
Rev. 1.1 — 19 June 2018
345311
48 of 62
Note:
The AGC only measures the Rx voltage level of the RxP. Normally the voltage
level at RxN and RxP should be the same. However, in case of wrong assembly
or a bad symmetry the voltage level might be different at both pins. Therefore, a
voltage measurement might be useful to ensure symmetry of the antenna tuning
and layout.
Note:
The voltage measurement at the RxP and RxN pins must be done with low
capacitance probe (active probe) with an input capacitance of < 3pF.
4.6 Test and debugging
Typically, the Rx does not require any specific optimization. However, in some critical
cases it might help to check the register settings. In any case it is very useful to ensure
the correct signal to noise level. In some cases, it might be required to reduce the
external noise level.
AUX1 & AUX2 can be used for analog test signals, the IRQ, AUX1, AUX2 and GPIO1
can be used for the digital test signal,
Note:
Be aware that some of those test pins might be used for other purpose already
(like IRQ)!
4.6.1 Digital test signals
The ENABLE_TESTBUS_DIGITAL command can be used to route any of the given
digital test signals to one of the output pins (see [1]).
Note:
Be aware that the test bus must be enabled to allow the test signal access: refer
to TESTBUS_ENABLE, EEPROM address 0x17. Be aware of the BUSY line
restrictions, in case the test bus in enabled.
However, the NFC Cockpit support the direct routing of test signals to the test pins as
described in [9].
4.6.2 Analog test signals
The analog test signals can be routed to the Pins AUX1 and AUX2, using the
ENABLE_TESTBUS_ANALOG command.
Note:
Be aware that the test bus must be enabled to allow the test signal access: refer
to TESTBUS_ENABLE, EEPROM address 0x17. Be aware of the BUSY line
restrictions, in case the test bus in enabled.
However, the NFC Cockpit support the direct routing of test signals to the test pins as
described in [9].
The most relevant test signals are the filtered and unfiltered I- and Q-Channel signals
and BPSK_SUM signal as shown in Fig 44.
