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SN65HVD75: R output issue

Part Number: SN65HVD75
Other Parts Discussed in Thread: SN65HVD72

Hi TI Expert,

   in our simple point to point RS485 communication using your SN65HVD72, we are facing the same issue on R pin as reported here ((+) SN65HVD75: SN65HVD75: Output issue - Interface forum - Interface - TI E2E support forums)

We saw the topic was closed/moved to direct communication via mail.

Could you provide the final solution of the problem?

Just for your info: our schematic is really close to the one in the ticket, the connection is point to point, we run at 115200bps N81, 

In our case the R pin goes down for 400ns (see the picture)

Many thanks

Federico

  • Hi Federico,

    I don't have the final solution to a thread that was closed 3 years ago unfortunately since its not online. 

    If the schematics are not identical it would be very helpful to share as small changes can make large impacts on the signal - and also if you could elaborate on what you are trying to achieve - as the schematic in the other post is using an implementation that may not be the best way forward with your application. Also I will say - if it is similar enough to the last application - the issue is not with the part its how you are using it - i.e. the scope shots show the receiver reacting to noise on the bus - which means that the receiver is active during this period and will pick up signals like that as the device has relatively low thresholds. 

    Please  let me know.

    Best,

    Parker Dodson

  • Hi Parker,

       thanks for you quick reply.

    In our case the schematic has a double LCL filter. We tested with and without it but no changes, the 101 sequence on Rout is still present. 

    We notice (on the limited numbers we have in R&D) the problem is present with components having a different marking code.

      Componet with problem: HVD72 - 12M - A8VX G4

      Component without problem: HVD72 - 09K - C9J6 G4

    We replaced the components and we saw the problem follows the components.

    Let me know if these info help you.

    Thanks

    Federico

  • Hi Federico,

    Can you confirm the OPN (the part number + the extra characters that denote package) such as SN65HVD72D or SN65HVD72DGKR for example - I just want to double check something internally. It does seem like these are possibly counterfeit devices (the date code that is breaking) - but I want to double check to make sure I am not missing something in my internal system.

    Please let me know.

    Best,

    Parker Dodson

  • Hi Parker,

      sorry for the delay but I was in a business trip. Yes we confirm the part number you see in the pictures.

    Regards

    Federico

  • Hi Federico,

    Yes - so these are most likely counterfeit devices - please see information here for next steps: https://www.ti.com/support-quality/quality-policies-procedures/anti-counterfeit.html

    Best,

    Parker Dodson

  • Hi Parker,

       I'm quite surprise about this. Anyway I have passed all the info to our Quality dept and they will take the lead for the next actions.

    Thank you for the support!!

    Federico