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TCA9517A: Datasheet specification inquiry

Boyan Lu
Expert 7005 points
Part Number: TCA9517A

Tool/software:

Hi team

My client has some questions about how the datasheet specifications should be viewed.

1. The customer said that VIL VIH VOL VOH these parameters have a maximum value and a minimum value or an intermediate value. Which one should be compared to be correct, or should it be within this range? In addition, why do some have only maximum values ​​and no minimum values?

2. Can you also help explain what VLC is?
3. And why does VLC have 0.45 and 0.4, which value should customers look at?

Thanks,

Boyan

  • 0
    TI__Mastermind 47188 points

    Hi Boyan,

    Boyan Lu said:
    1. The customer said that VIL VIH VOL VOH these parameters have a maximum value and a minimum value or an intermediate value. Which one should be compared to be correct, or should it be within this range? In addition, why do some have only maximum values ​​and no minimum values?

    When designing in this device, I recommend design for max / min conditions. 

    Some only have maximum values according to the I2C standard. For example VIL only has maximum because you must be at or below 30% of VCCA in order to be considered a LOW by the device. The minimum spec is technically GND, as it is assumed that voltage will not go past ground. Abs. max has the negative voltage spike on the input to be -0.5V which any further could cause potential damage to the device due to violating abs. max spec.

    Boyan Lu said:
    2. Can you also help explain what VLC is?

    VILC is the minimum voltage that is required to pass a LOW from B-side to A-side. 

    VILB = VILC. The target on B-side must be able to pull the bus low to a VOL < VILC = 0.45V. 

    Boyan Lu said:
    3. And why does VLC have 0.45 and 0.4, which value should customers look at?

    This is a datasheet error. I submitted a ticket for the revision. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    TI__Expert 7005 points

    Hi Tyler

    Thank you very much for your detailed explanation.

    Regards,

    Boyan

  • 0 in reply to Boyan Lu
    TI__Mastermind 47188 points

    Hi Boyan,

    Glad I could help. If you have any more questions, please feel free to reach out. 

    Regards,

    Tyler

  • 0
    Prodigy 150 points

    HI Tyler

    here is Tommy from ACCTON

    I have some question for the TCA9517A spec

    in the befoe we use the spec like picture below

    TCA9517A

    input VIL Aside

    input VIH Aside

    <0.3VCCA

    >0.7VCCA
    <5.5V

    TCA9517A

    ouput VOL Bside

    >0.45V

    <0.6V

    TCA9517A

    input VIL Bside

    input VIH Bside

    <0.45V

    <5.5V
    >0.7VDDB

    TCA9517A

    output VOL Aside

    <0.2V

    that inculding the VILC

    If there has any wrong, pleasw tell me

    Thanks

    Tommy

  • 0 in reply to Tommy Tuu
    TI__Mastermind 40036 points

    Hi Tommy,

    This looks correct. 

    Regards,

    Jack

  • 0 in reply to Jack Guan
    Prodigy 150 points

    Hi Jack

    I have some question for tca9517A

    ouput VOL Bside

    >0.45V

    <0.6V

    In our measurement it only0.39V and 0.42V


     
    it's that currect?

    Thanks

    Tommy

  • 0 in reply to Tommy Tuu
    Guru 316640 points

    How exactly did you test this? The TCA9517A itself will output more than 0.45 on the A side, but other devices can pull the lines lower.

  • 0 in reply to Tommy Tuu
    TI__Mastermind 47188 points

    Hi Tommy,

    VOLB is >0.45V and <0.6V across voltage and temperature. 

    Same question as Clemens here... how was this measured? This seems incorrect. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 150 points

    we use the 1.8V(PULL UP 1K ohm) and shifting to 3.3V(PULL UP 1K ohm)

    in the sumulation, it can meet the spec on VOLB

    but in the measurement result is lower than 0.45V

    That is werid. here is the measurement picture

    we probe it on IC.

    Thanks

    Tommy

  • 0 in reply to Tommy Tuu
    Guru 316640 points

    What voltages are applied to the signal lines? If there is I²C communication going on, then all devices are pulling the lines low at some time, and you will see lower voltages.

  • 0 in reply to Clemens Ladisch
    Prodigy 150 points

    We use th 1.8V  to signal lines and want ro change to 3.3V

    so u mean in the difference situation

    the measurement will lower than 045V

    But in simulation we doesn;t see this issue

    Thanks

    Tommy

  • 0 in reply to Tommy Tuu
    TI__Intellectual 1150 points

    Hello

    The team is currently on Thanksgiving holidays. Pls expect response delay till Dec-2nd. Thank you for your patience.

    BR

    -Yuan

  • 0 in reply to Tommy Tuu
    TI__Mastermind 47188 points

    Hi Tommy,

    The datasheet specifies that when driving a LOW from A-side to B-side, VOLB is at least 0.45V up to a max of 0.6V output voltage when IOL is between 100 uA and 6 mA of loading (this loading changes depending on the equivalent pull-up resistance on B-side). 

    What Clemens is talking about is the scenario that some peripheral I2C device on the B-side is driving the bus LOW. The output low voltage on B-side could be lower than 0.45V depending on what device is driving the LOW. 

    If you are certain that communication is occurring from the buffer by driving a LOW on A-side first, then B-side drives LOW, then this is the buffer driving the LOW in which the voltage should be between 0.45V and 0.6V as long as the IOL, ambient temperature, and VCCB voltage is respected according to the datasheet test specs. 

    Do you have scope captures of the measured voltage? Would there be any error in the measurement on the scope? Are the scope probes calibrated? 

    Has this been repeated across multiple TCA9517A's? 

    Regards,

    Tyler