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TCA9517 - Guaranteed spec for VIL (MAX) without bus contention --> VILC

Kawai
Guru 19775 points
Other Parts Discussed in Thread: TCA9517, PCA9517

Hi Team,

I see similar posts, however, please allow me to post to clarify the TCA9517 requirement.
Below are the datasheet descriptions. Here, I have two questions.
Without the maximum value of VIL(B-side), customer would not be able to design system which operation is guaranteed.

[Q1]
What is the maximum VILC accepted for TCA9517 to avoid bus contention ?
We need to clarify what is the guaranteed voltage so that customer system would not have any problem.

If VILC=0.4V is the MAX instead of TYP, please let us know.
However, VOL_MIN - (VOL-VILC_TYP) is 0.38V. Regarding this spec, I was thinking that required VILC may be lower than 0.4V.

[Q2]
Why is "VOL-VILC" spec stated for ? It is also confusing that calculation result is not matching. (0.52 - 0.070 != 0.40)
I believe it is described to let user know the lowest voltage what TCA9517 can operate without any problem.
However, we need the worst condition information.

Best Regards,

Kawai

  • 0
    Guru 19775 points

    Hello Team,

    Below is competitor datasheet (NXP PCA9517). This is also not clear, however, MAXIMUM VOL-VILC is guaranteed as 70mV (MAX).
    Based on this number, one could understand that "MAX VILC = 0.40V". (Although the number is listed in the typ)

    Could you please tell us the MAX value for "VILC" or "VOL-VILC" ??

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    TI__Expert 4525 points

    Hi TI expert,

    Can you help to answer the question for Kawai-san on this thread?

    Or take this offline for more information if needed.

    Thank you and best regards,

    Daisuke KAWASAKI

  • 0 in reply to daisuke kawasaki
    TI__Genius 16430 points
    Kawasaki-san,

    My appologies for the delay, I am currently out of the office traveling and our other contact is on vacation. We will respond to you shortly.
  • 0 in reply to Jonathan Valdez
    TI__Expert 4525 points

    Hi Jonathan-san,

     

    Can you follow up if you are available now?

     

    Thank you and best regards,

    Daisuke KAWASAKI

  • 0 in reply to daisuke kawasaki
    TI__Genius 16430 points
    Kawasaki-san,

    My apologies for the delay. The applications team has been traveling.


    I agree that your comment about the differences in spec.

    A lot of the values in the datasheet are to provide some margin.

    The way we characterize these parameters is by testing them independently.

    I dug through all the simulation data I have for this part, and from what I can tell, VILC is typical 0.4 V. WE do not have a maximum, as it is bounded by the VOL of the device.

    I cannot find information on the VOL-VILC spec, however, based on some of the IP it shares from other devices, I believe it actually is 70 mV maximum, not typical. This would make the max VILC 0.6 V - 0.07 = 0.53 V depending on the VOL.
  • 0 in reply to Jonathan Valdez
    Guru 19775 points
    Hello Jonathan-san,

    Thank you for your reply. Please allow me to double check.
    Can you commit the TCA9517 will operate without any problem as long as customer designs "FPGA output VOL under 0.4V on B-side" ?


    I believe the worst VOL requirement from the device on B-side is the following.

    If VOL-VILC = 70mV (MAX),
    VILC (MAX) = VOL (MIN) - 70mV (MAX) = 0.450 - 0.070 = 0.38V

    So the CPU or FPGA on the B-side must have VOL lower than 0.38V.

    Regarding the answer VILC is 0.6V - 0.07 = 0.53V, so the VIL spec can be taken as it is relaxed.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    Guru 19775 points
    Hello Jonathan-san and Team,

    What is the acceptable maximum input LOW signal level on B-side which TCA9517 could guarantee its operation ?

    In other words, what is the input voltage level on B-side that may cause TCA9517 communication error ?

    Could you please suggest us the design guideline ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Genius 16430 points
    Since the VILC value varies depending on the VOL of the device, you should go on the 'safe' side of it and do VOLmin- 70 mV = 0.45 - 0.07 = 0.38 V.


    0.38 V should be a safe max, because it's the lowest the VILC value might go, so it is the maximum that you should not cross to be safe.
  • 0 in reply to Jonathan Valdez
    Guru 19775 points
    Hello Jonathan-san,

    Thank you for your answer.

    I will answer customer to design VIL signal lower than 0.38V for safe operation.

    Best Regards,
    Kawai