PN532 reduced range at low temperature

[grayscales]

Good morning,

My name is Inigo and we have designed a board to read RFID tags with the PN532. We have been using it for one-two years and it has been working correctly in ambient temperatures of +10ºC. Now we have started to sell our product for colder environments (-10ºC to 0ºC) and the range of detection of RFID tags has been reduced dramatically. Normally we would detect a tag around 40-65mm from the antenna when at 20ºC ambient. But when we lower the temperature to around -5º/0ºC its range goes down to 5-10mm if it detects the tag at all. All our components are rated for -20ºC/-30ºC and the ones used for the impedance matching show no change in impedance over that temperature range. Here is the relevant schematic:

The antenna is connected to a 3 pin header and it is an external PCB antenna. We have also tested the PCB in low temperature and the PCB antenna at room temperature and the results are the same.

We have read the datasheet and tried to find some documentation about the effects of low temperatures on the chip. But we have not found anything relevant yet. Is there something specific we should look into to finde the problem in low temperatures?

Thank you for your help and best regards,

Inigo

[renkebienert]

Hi Inigo,

question would be: what actually limits the read range?

Power? TxData? or RxData?

A read range degradation (rather than a total stop of working) normally is linked to analog behavior, which changes due to tolerance (or better temperature shift). In most of the cases the analog (i.e. antenna tuning) components are linked to that.

BR,

Renke

[grayscales]

Hello Renke,

A colleage of yours got in contact with me and we managed to find the problem. The matching circuit was not properly matched and I tuned it to get a better response eliminating this range degradation with temperature.

Best regards,

Inigo