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TCA9617A: I2C bus stub too long

user3317283
Prodigy 100 points
Part Number: TCA9617A
Other Parts Discussed in Thread: TCA9509

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)?

  • 0
    TI__Mastermind 49040 points

    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

  • 0 in reply to BOBBY
    Prodigy 100 points

    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?

  • 0 in reply to user3317283
    TI__Mastermind 49040 points

    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