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TCA9548A: SDA rise time

Part Number: TCA9548A

Hello,

Our customer use the TCA9548A with Fast mode.

The customer can not follow the specification of the SDA rise time. The value of the customer is 400ns.

But it is followed the setup and hold time with SCL and SDA.

Is it possible to communicate HOST and the TCA9548A?

Best Regards,

Naoki Aoyama

  • Hello Naoki,
    It sounds like your saying they can't meet the 300ns max rise time outlined in the I2C specification for Fast Mode. Have they put a buffer in series with the TCA9548A? Can I have a schematic so I can see what they are doing and give recommendations? I can't guarantee the part will work if they violate the I2C specifications. That is what we design and test our parts to. Have they considered going to a standard mode? Do they need the faster data rate? In all likely hood it will work but we can't guarantee that.
    -Francis Houde
  • Hello Francis,

    Thank you for your reply.

    I attached the circuit of the customer.

    TCA9548A_Application.pdf

    Could you give me any advise?

    Best Regards,

    Naoki Aoyama

  • Hello Naoki,
    Did the customer lower the pull up resistance? If so, to what value? If your slave and master devices have low VIL then this might be a problem. You really need to have a buffer to isolate the capacitance.

    Also, are they turning on ALL the channels? This schematic doesn't show what is on the other side of the Switch/Mux.

    Is this a harness they are using? What does FCC1 and FCC2 mean in the diagram.

    -Francis Houde
  • Hello Francis,

    Sorry, it is typo. That is FFC, not FCC.
    The driveability of the HOST is poor, I'll suggest the customer using buffer.

    Thanks,
    Naoki Aoyama