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ISO1452: part-to-part skew of driver and receiver

Jeroen van der Velden
Prodigy 140 points
Part Number: ISO1452
Other Parts Discussed in Thread: ISO1450

Dear TI team, 

For a new product design I am going to implement a multitude of ISO1450 and/or ISO1452 isolated RS-485 transceivers in parallel. The application requires the skew between any of the drivers to be less than 10ns. Unfortunately, the datasheet does not specify the part-to-part skew of the driver and receiver. Do you have this information available somewhere? All devices will be powered with the same voltage level. Ambient temperature will be approximately +35 Celsius degrees. 

Hope you can help me.

Best regards,
Jeroen

  • 0
    TI__Mastermind 24975 points

    Hello Jeroen,

    We do not have this information immediately available. 

    Based on the switching characteristics for the 50Mbps devices (ISO1450 and 1452), the propagation delay listed would give the absolute worst case scenario range. 

    Are you referring to the driver side skew, the receiver side skew, or both need to meet the 10ns spec?

    On the driver side the tpd worst case is 41ns with typical 19ns, so this alone would not support 10ns part to part skew, however if its all powered from the same supply and at a fixed temperature all the time, then 10ns may be achievable. 

    The receiver side specification is not as tight as the driver, so do you need this to meet the 10ns as well?

    We would need additional time to assess whether or not this would be achievable and would only be able to give you a sense of if its possible, however we would not be able to fully guarantee the 10ns part to part skew spec. Would further insight on this topic be good, or will you need it to be 100% guaranteed?

    Best,
    Michael

  • 0 in reply to Michael J Schultis
    Prodigy 140 points

    Hello Michael,

    Thank you for your prompt response.

    The 10ns spec is solely for the driver side skew. To know the receiver side skew would be nice for future applications.

    Like you, I also believe that the driver skew is probably much better (< 10ns) when all devices experience the same operational conditions. 

    I understand TI cannot 100% guarantee the 10ns part-to-part skew, but even to know there's a fair chance the 10ns can be met would be very much appreciated. Let me know if you need more information to assess whether or not the 10ns skew spec may be achievable. 

    Many thanks in advance.

    Best regards,
    Jeroen

  • 0 in reply to Jeroen van der Velden
    TI__Expert 8030 points

    Hi Jeroen,

    Thanks for confirming that you are primarily interested in the driver side skew. 

    This data is not readily available, but we can look into providing an estimation for this parameter. Please allow us until Wednesday of next week to look into this. 

    Regards,

    Kenneth

  • 0 in reply to Kenneth Arnold
    TI__Expert 8030 points

    Hi Jeroen,

    Thank you for your patience.

    Jeroen van der Velden said:
    I understand TI cannot 100% guarantee the 10ns part-to-part skew, but even to know there's a fair chance the 10ns can be met would be very much appreciated. Let me know if you need more information to assess whether or not the 10ns skew spec may be achievable. 

    I went ahead and reviewed our internal test data for this device. Based on our test data, we estimate that the driver side part to part skew should remain under 10 ns during device operation. Please note that this is only an estimation, as we cannot guarantee any specifications that are not listed in the device datasheet.  

    Regards,

    Kenneth

  • 0 in reply to Kenneth Arnold
    Prodigy 140 points

    Hi Kenneth,

    Thank you very much for your time and effort. I am pleased to hear that the estimated part to part skew is under 10ns. An estimate will do for us. 

    Thanks again and best regards,

    Jeroen