Hi everyone!
I am currently testing the reading of a tag with an ST25TV02K chip using two different readers. Both readers are based on the same NFC chip and use the same antenna coil, but they differ in the matching network between the NFC chip and the antenna.
In theory, the first reader should be better matched to the NFC chip, while the second reader should be less well matched (and therefore expected to deliver less power). I have verified the reader matching using a VNA. However, I am observing an issue: at the same tag-to-reader distance and with the same power settings, tag read/write operations with the ST25TV02K sometimes fail when using the better-matched reader.
This makes me wonder whether the better-matched reader might actually be delivering too much power to the tag, such that the VAC0–VAC1 voltage exceeds the maximum limit, preventing the ST25TV02K from responding correctly. Conversely, the less well-matched reader could be delivering lower power, keeping VAC0–VAC1 within the allowed range, which results in stable tag reading.
Does anyone know if this interpretation makes sense? And if so, is there any documentation or reference material that explains this behavior in detail?
