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TMP75C-Q1: During communication with the master

Koji Hayashi92
Mastermind 7030 points
Part Number: TMP75C-Q1
Other Parts Discussed in Thread: TMP75

Hi TI-team

My customer have a question.

If the I2C pull-up power is cut off (cut off without a stop condition) while the TMP75C-Q1 is communicating with the master, what effect will it have on the TMP75C-Q1 ? 

 

Best Regards,

Koji Hayashi

  • 0
    TI__Genius 9675 points

    Hi Koji,

    If the I2C pull-up power is cut off the TMP75C-Q1 will reset the communication if the timeout is exceeded. You can see more details of the timeout function in section 7.3.3.6 of the datasheet. 

    The TMP75C-Q1 would be ready to continue in normal operation once the power comes back up.

    Jalen

  • 0 in reply to Jalen Tate89
    Mastermind 7030 points

    Hi Jalen-san

    Thank you for quick response.

    >If the I2C pull-up power is cut off the TMP75C-Q1 will reset the communication if the timeout is exceeded.

    At this time, isn't there a trouble mode such as a failure on the temperature sensor side just by resetting ?

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    TI__Genius 9675 points

    Koji,

    To be clear the serial interface is what is reset– not the temperature sensor. Insert from the datasheet on the timeout function below:

    "The TMP75C-Q1 resets the serial interface if SCL or SDA are held low for 22 ms (typ) between a start and stop condition. If the TMP75C-Q1 is pulled low, it releases the bus and then waits for a start condition. To avoid activating the timeout function, it is necessary to maintain a communication speed of at least 1 kHz for the SCL operating frequency."

    Jalen

  • 0 in reply to Jalen Tate89
    Mastermind 7030 points

    Hi Jalen-san

    Thank you for quick response.

    SDA, SCL, ALERT, etc. that have been pulled up become LOW and are only reset, and TMP will not be broken or in abnormal mode.
    Is it correct ?

     

    Best Regards,

    Koji Hayashi

  • 0 in reply to Koji Hayashi92
    TI__Genius 9675 points

    Koji,

    The SCL is controlled by the host/master. Once SCL goes low the timeout counter starts. After ~22ms (typ) the TMP75 will release the bus. In the case that power is off.. these pins would be left floating. The TMP75 will then wait for the next start condition.

    The TMP75 will not be broken or in an abnormal mode.

    Jalen