[问答]

为什么Zrx调谐ST95HF要调整到低于7V？

问答对人有帮助，内容完整，我也想知道答案 0 敬启者，我们根据您的ST95HF生产了超过10000个NFC读卡器，其设计基于您的参考设计EVAL-ST95HF。我们在一小批电路板上遇到了读取距离问题，我已经尝试过测量天线的广告，看起来不错，即使标签检测程序正确启动，但我们无法读取或写入标签在最大距离。由于该领域似乎很好，在我看来这似乎是RX方面的一个问题，所以我试图将阻尼电阻Zrx从默认的330Ohm降低到220Ohm，现在看起来一切正常。我在AN4327中发现了一些参考值，应该定义这些值以将Vrx1-Vrx2电压降低到7V以下，看起来这个电压可以在引脚ST_R0上采样，新的Zrx值此电压达到9V，数据表说最大限制为18V。所以我认为是安全的，但我不明白为什么这个级别应该调整到低于7V，我想保证这个修改不应该引入其他副作用。以上来自于谷歌翻译以下为原文 Dear sirs, we have produced more than 10000 pcs of NFC readers based on your ST95HF the design is based on your reference design EVAL-ST95HF. We experience on a small batch of boards a problem in the reading distance, I have already tried to measure the field of the antenna ad it seems good, even the tag detection procedure starts correctly, but we are not able to read or write the TAG at the maximum distance. As the field seems good, in my opinion it seems a problem in the RX side, so I have tried to reduce the damping resistor Zrx from the default 330Ohm to 220Ohm and now all seems to work fine. I have found some references in the AN4327 that the values should be defined to reduce the Vrx1-Vrx2 voltage below 7V and it seems that this voltage could sampled at pin ST_R0, with the new Zrx value this voltage reaches 9V, and the datasheet says that the maximum limit is 18V. So I suppose to be on the safe side, but I don't understand why this level should be tuned to less than 7V, and I would like to be shure that this modify should not introduce other side effects. 0
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答案对人有帮助，有参考价值 0 你好Gabriele，如果您正在调整ac0和ac1之间低于18Vpp的电压，您的设计可能是安全的。接收器输入RX1和RX2通常通过两个外部衰减电阻连接或电容器以避免内部检测器饱和这两个串联电阻器RRX1，RRX2必须进行调整以避免进入钳位区域它们定义的RX路径衰减可能低于9V（参考数据表）.7V是安全的用于原型修整的保护带，考虑到调整公差。问候 PYB 以上来自于谷歌翻译以下为原文 Hello Gabriele, If you are adjusting the voltage lower than 18Vpp between ac0 and ac1 your design might be secure.The receiver inputs RX1 and RX2 are typically connected through two external attenuation resistors or capacitors to avoid saturation of the internal detector Those 2 serial resistors RRX1, RRX2 have to be adjusted in order to avoid entering the clamping region They are defining the RX path attenuation which might be lower that 9V (Ref Datasheet.) 7V is a secured guarband for prototype trimming considering tuning tolerances. Regards PYB

2019-7-22 16:17:33 评论举报刘峰