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PCA9517 what is a trigger to switch buffer ?

Taichi Noda
Expert 1350 points
Other Parts Discussed in Thread: PCA9517, TCA9517

Hi,all

Please let me ask a question about PCA9517.

When master device read a data of slave device ,  there is a diffrence between SDAA and SDAB as following diagram.

In this case, direction should be master to slave under normal circumstances , however a direction is slave to master ,

I think this is a cause . What is a trigger to swtich buffer ?

 

I am looking forward to your reply.

Best regards.

Taichi

 

 

  • 0
    Expert 1350 points

    Hi,All

    Could you any comment about this question ?

    Which driver on figure 1 is A - side driver ?If  I get this answer , I may  be able to understand a trigger to swtich buffer after reading datasheet  P2 .

    I am looking forward to your reply.

    Best regards.

     

     

     

  • 0 in reply to Taichi Noda
    Expert 1350 points

    Hi,all

    I got a peripheral circuit information as following diagram.

    Is there any solution to communicate well ?

    I think a voltage from slave must be lower than 0.4V ,however how much is right resistance ?

    Best regards.

  • 0 in reply to Taichi Noda
    TI__Mastermind 30280 points

    Taichi,

    In the short term, I would like to point out that the PCA9517 is Not Recommended for New Design (NRND) and has been replaced by the TCA9517 which is a pin-2-pin drop-in replacement.

    Also, for now, I would like to point out that there is an offset voltage on the B-side of this device that may be causing problems in your architecture.

    I am not sure I understand your question fully enough to answer specifically. Can you give some examples of the issue or take some oscilloscope pictures to help me understand?

    -Brian

  • 0 in reply to Brian Berner
    Expert 1350 points

    Hello Brian

    As you pinpointed , an offset voltage on the B-side of PCA9517 seems to cause problems.

    I got secrency oscilloscope pictures from customer so could you teach me your company mail adddess ?

    I think mailing that to you.

    Best regards.

    Taichi

    My company address is following.

    noda-t@clv.macnica.co.jp

     

     

  • 0 in reply to Taichi Noda
    Expert 1350 points

    Hi,Brian

    Could you reply this post ?

    I am looking forward to your reply.

    Best regards.

    Taichi

     

  • 0 in reply to Taichi Noda
    TI__Mastermind 30280 points

    Taichi,

    Is it possible for you to sketch/re-draw the oscilloscope pictures to give an example of the issue?

    If not, please contact your local TI sales team member, as it is not customary for forum posts to be resolved via direct e-mail.

    Regards,

  • 0 in reply to Brian Berner
    Expert 1350 points

    Hi Brian

    I posted a block diagram and wave forms to the following.

    Under normal circumstances, I think PCA9517 should be set reversely.

    In this case ,this system is operated normally ? If not ,are there any countermeasures ?

    I am looking forward to your reply.

    Best regards.

    Taichi