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TCA9517-Q1: Oscillation issue for two B-side of TCA9517 facing same I2C bus.

Part Number: TCA9517-Q1
Other Parts Discussed in Thread: TCA9509, PCA9306, TCA9517

Hi

Does  it can cause oscillation  if we have two B-sides of TCA9517s facing the same I2C bus?

Do you have any suggestion if we need design that 3.3V I2C BUS connect to two 1.8V I2C.

Best Regards

Frank

  • Having two static voltage offset devices connected in parallel can cause oscillations.

    Can you place a TCA9509 in place of one of the TCA9517s? A side should be facing the 1.8V and B side should be facing the 3.3V (I assume currently the 3.3V side is where the B sides are connected). Are there any other I2C buffers on the 1.8V side?

    -Bobby

  • Hi Bobby,

    Thank you for your suggestions.

    Does it have AECQ parts or other solution could meet AECQ?

    Regards

    Frank

  • Our only I2C automotive qualified buffer is the TCA9517. We do have a PCA9306 level shifter that is automotive qualified but its not pin to pin and I can't say if it would be a good part to replace the TCA9517 without seeing a block diagram of the I2C system.

    -Bobby

  • Hi Bobby,

    As my topology, I have one 3.3V I2C bus that connecting two level shift TCA9517(B-Side) to change level to 1.8V from 3.3V bus level.

    If I replace one of TCA9517 to PCA9306. B-side of PCA9306 connect to 3.3V bus from master, A-side connect to 1.8V device.

    Is it be workable?

    Frank

  • B side has a ~540mV offset, if the VoL of B from TCA9517 is larger than the ViL of the 1.8V device then it may not recognize it as a low. The PCA9306 is a level shifter so it will not redrive the signal. This may be a problem if I am understanding the set up correctly.

    -Bobby