PN7150 vs Temperature

[deborah_linzi]

Hi everybody,

I'm using PN7150 and a bare metal MCU running the nxp library provided in the SW4325 example.

Everything is working fine at room temperature but it suddenly report an error when the temperature fall below 0°C. The reading process start again properly as temperature drop further and gets below -10°C or, of course, at any temperature above 0°C. It looks like there is a range between 0°C and -10°C where something doesn't work properly

The message  reported is:

- POLL MODE: Remote MIFARE card activated
SENS_RES = 0x04 0x00
NFCID = E3 30 0B BC
SEL_RES = 0x08
Authenticate sector 0 failed with error 0x03

Some more pieces of information, antenna is printed on pcb, using a probe loop connected to an oscilloscope I can not see any drop in signal strength, at any temperature, I only see a different packet length, longer when it reads the information I need , sector 0, block 1 and 2.

Does anybody experienced a similar phenomena, any suggestions?

Thanks in advance

Deborah

[vicentegomez]

Hi

Did you check that there is not a manufacturing problem like an open pin or component damage?

The PN7150 is controlled by a MCU, would it be possible to know the MCU part?

Would be possible that you test it using the evaluation board?

Regards

Vicente Gomez

[deborah_linzi]

Hi,

thanks for your answer, we have 10 boards and on all of them we have the same issue, we checked for manufacturing defect  but as long as we can see using a microscope everything seems to be ok. 

Anyhow, I'm using an STM32L486 MCU on a board that includes the PN7150, along with the antenna, matching has been tuned using a VNA, sensitivity is very good, everything is working fine but the temperature.

I have also connected the EVB to my MCU  keeping the MCU board outside the temperature chamber, same issue.

The only one thing I should mention is that on the EVB the quartz was replaced, I can't remember why, I'm going to buy another EVB so that every parts will be original.

Regards

Deborah

[vicentegomez]

Please let me know the results on the EVB

[deborah_linzi]

Hi,

an update on my issue.

We did some more tests, I will try to summarize them here.

1) I have connected the eval board to our board, I2c, IRQ,VEN and 3.3V, it is working fine, at any temperature.

2) I have connected my antenna and my matching network to the PN7150 on the eval board, it is working fine.

3) The other way around, antenna and matching networkfrom the eval board connected to the PN7150 on my board, it fail at -5°C.

4) I have populated a board with only the NFC, the antenna and the matching network (just like an eval board). Connect it like the point 1) but it doesn't work.  

5) It seem quite straight forward that the problem is on the PN7150 locate in my board, may be some soldering issue. I dismounted the PN7150, I cleaned up the area and I mounted again the same PN7150, now I'm sure it is soldered correctly but it is still failing. I replaced the PN7150, even if, it is most likely  coming from the same lot, and all the passive components but there is no way to get the circuit working between -5°C an -8°C.

Any suggestion is more than welcome

Deborah

[vicentegomez]

Did you check if you do not have any problem with the external components like a capacitor, resistor etc

Maybe you have a wrong capacitor value 

I hope this will help you.

[deborah_linzi]

Hi Vicente,

After weeks of test I just want to report how the problem was solved, may be it can help someone else. As suggested by you the problem was assembly process related. From one side the solder paste was in some way not able to guarantee a complete adhesion to both passive and active components, from the other side, the step that solved most of the problems was to add a cleaning phase right after the soldering step. Even if the solder past was a no clean past there was some flux residual that at particular temperature was somehow having quite a significant impact on RF performances. This is not unusual, I sow it many times working with several GHz but I was simply surprise to have this effect at low frequency. There is always something to learn.

Deborah

[vicentegomez]

Hi

Excellent news and thanks for the sharing

Take care

regards

Vicente