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TCA9509: 关于I2C电平转换芯片的B端的SDA波形异常，出现了半高电平

baoling wang
Prodigy 20 points
Part Number: TCA9509

如图所示，芯片用的是TCA9509DGKR  内部A端I2C有上拉，B端无上拉（需要外部上来）实现1.8V转3.3V的I2C电平转换。I2C挂载设备后，发现了A端的SDA波形异常，出现了半高电平状态，B端的SDA是正常的。于是做了多次交叉实现，如更换电阻的匹配（从1.5-2.2-3.3-4.7-5.1-10K）都无效，SDA依然拉不低。最终判断就是I2C电平芯片引起了，但是不知道具体原因。