PN7160 RX-AGC TARGET LEVEL

[coccokun-1]

I am designing an NFC reader device using the PN7160.
Based on the receive path design specified in AN132198 (PN7160 Antenna Design and Matching Guide), I verified the level input to the receive port.
The document states it should converge to 1.6Vp-p, but for some reason, it converges to 1.2Vp-p in my environment.
Since the voltage is approximately 2Vp-p before AGC operation, it appears the AGC is adjusting to achieve 1.2Vp-p.
When testing by significantly reducing the resistor value to push it outside the AGC range, it can be adjusted to 1.6Vp-p.
I understand setting an AGC target voltage is unnecessary, but was there an option to set it?

If anyone knows, please advise.

Thank you in advance.

Translated with DeepL.com (free version)

[Tomas_Parizek]

Hello @coccokun-1 , 

The recommended way is to enable continuous RF Field, e.g., with the help of the NFC Factory Test Application, and measure the peak voltage between RXN (or RXP) and GND. This voltage should be around 1.6Vp as described in the app. note. 

Once the IC is in the functional mode (NFC Polling), the AGC is active and regulates the RX voltage amplitude. 

If you don´t have an option to activate the continuous RF field. I would try to keep 2.2K and measure the voltage for unloaded and loaded scenarios (place an NFC card and then the mobile phone in the antenna proximity). You should see that the voltage is still in the range of 1.2Vp-1.6Vp, and you don´t see any issue with the reception. 

BR

Tomas 

[EduardoZamora]

Hello @coccokun-1

Hope you are doing well.

What is the value you are using for the series resistor (Rrx)? The serial value resistor Rrx could be in the range of 1 kΩ to 10 k, and Low Rrx -> Higher VRx voltage.

Also, perhaps you may find some useful information in the PN7160 RF settings guide.

Regards,
Eduardo.

[coccokun-1]

Thank you for your reply.

I have set Rrx to 2.2kΩ.
I also tried 1kΩ, but when the AGC value is Static, it shows over 2Vp-p. However, when AGC activates, it converges to 1.2V.
Functionally, it seems like AGC is trying to converge the reception level to 1.2Vp-p.

Due to limitations of the available firmware, I'm checking the level in normal polling operation, not test mode.
Is the 1.6Vp-p mentioned in the documentation the value before AGC activates?

I appreciate your advice.

Thank you