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TCA9617A: I2C bus stub too long

Part Number: TCA9617A

Currently our I2C bus/PMbus (between BMC and PSU) has "master-abnormal stop-start" issue, some PSU bus information can't be read out sometimes. We have four BMC connected to PSU, then the I2C bus stub is long,  the I2C clock waveform has a drop when clock rise from low state to high state. Now I want to reduce the stub to reduce the reflection, I tried 9617A, it seems not good, any other chip can be used to reduce the stub (cut the I2C bus completely)?

  • Hello,

    Can you provide scope shots of the the issue you are seeing?

    What is the Vcc range you are using?

    What is the max clock frequency?

    Thanks,

    -Bobby

  • In reply to Bobby Nguyen:

    Thanks for your reply, I just debugged that the issue is caused by four PCA9617A port B are connected together. How about TI chip, two chips port B can be connected together? or it is prohibited?

  • In reply to user3317283:

    Hello,

    "How about TI chip, two chips port B can be connected together? or it is prohibited?"

    -This is prohibited. We do have a device that has the "offset" side on A instead of B (TCA9509) but keep in mind this device wants VccB to be atleast 1V higher than VccA. It also requires NO pull up on A side. The only other thing about this device is it only supports up to 400kHz. (your device supports 1MHz).

    Thanks,

    -Bobby

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