PN7160: reduce range dynamically in software

[QuarterOpposite]

We're using the PN7160. This works very well, and in our application, we would sometimes prefer to reduce the range that the PN7160 reads tags from. To be clear, we would only like reading to work if you hold the tag closer; the problem is that the PN7160 works too well with the default settings and reads tags that are too far away.

There are a lot of different power/configuration settings. I've found a lot of documentation for how to increase the range by correctly tuning parameters, but which would be the best to adjust to *reduce* the range of the reader? We would like to be able to configure this from software.

Ideally, an answer would also include an example NCI message to send, but a general direction would also be helpful already.

[Tomas_Parizek]

Hello QuarterOpposite, 

As my collegue recomended, you can reduce the TXLDO voltage by changing the PMU config. You can even go for TXLDO voltage 2.7V

To configure the PMU config correctly, you can use our PMU configuration excel sheet which is available as part of the FAQ  Aplicatin Note. (AN13892) 

To further reduction of the power, you can also use a DPC and reduce/limit the number of DPC entries.

See this text -> 

https://community.nxp.com/t5/NFC-Knowledge-Base/PN7160-How-to-reduce-output-power-using-DPC-Reader-M...

BR

Tomas 

[QuarterOpposite]

Hi @Tomas_Parizek , thanks for the reply.

I changed the TXLDO voltage using the Excel tool, and also used the other Excel DPC tool to configure 1 entry with GSN of 0x01, but this unfortunately still is too close, I don't even notice a range decrease (it's about 45mm). If I set the GSN to 0x00, it stops working alltogether.

Are there other mechanisms to reduce the range?

[Tomas_Parizek]

Hello QuarterOpposite, 

Once you set GSN to 0x00, the TX driver is completely disabled. I would also recommend to stay with the GSN around 0x02 or 0x03. 

Value 0x01 might bring some instability due to the waveform deformation. 

Back to your question. The other option is to adjust the Rx path. You can try to reduce the Rx gain. It will reduce the reading distance as well.  The default value for RX gain is typically between 60dB-51dB. So you can try going down to e.g. 39dB or 32dB 

For more details, see the PN7160 RF Settings guide: 

BR

Tomas 

[danielchen]

Hi 

In the default settings, TVDD is configured as 4.75V, maybe you can try to configure it to 3.3v to see whether it helps.

Regards

Daniel