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TCA9509: I2C clock frequency be changed with TCA9509

Ben Kuo
Expert 7520 points
Part Number: TCA9509

Dear team,

We use TCA9509 for I2C buffer function, but I2C clock frequency and duty be changed after TCA9509.

Without TCA9509, I2C clock frequency is 400KHz and 50% duty. With TCA9509, frequency change to 390KHz and duty change to 45%.

May I know is this normal behavior for TCA9509? If not, what is potential root cause?

Regards,

Ben

  • 0
    Guru 302460 points

    The TCA9509 cannot change the frequency. The clock frequency is determined by the I²C master, and can be reduced by any slave with clock stretching. How did you measure the frequency?

    Due to the additional propagation delays, duty cycle changes are normal.

  • 0 in reply to Clemens Ladisch
    TI__Guru 73202 points

    Thanks for the help Clemens!

    Ben,

    Clemens can help, but I've also assigned this to an expert from TI. Please allow some delay in response due to US holidays.

    Regards,

    Eric Hackett