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SN55LVDS32-SP: Confirmation of the "Part-to-part skew" timing?

AnBer
Mastermind 28880 points
Part Number: SN55LVDS32-SP
Other Parts Discussed in Thread: SN55LVDS32, SN55LVDS33-SP

Team,

In case you want to use multiple SN55LVDS3x in the design:
-Can you please confirm that the "part to part skew" specification applies as well to SN55LVDS32-SP?
The SLLS262R datasheet gives Part-to-part skew(tsk(pp)) at page 10 for the SN65LVDSxxx family.
Is it valid as well for the SN55LVDS32 for the complete range of specification (-55C to 125C) ?
-If not do we have a rule of thumb of what could be the worst possible Part-to-part skew?

Thanks in advance,

Anthony

  • 0
    TI__Guru 62930 points
    Anthony,
    The silicon design for the commercial version and the military and space versions are virtually identical.
    The performance will be similar, with the exception of operating at extreme temperatures. Practically, this will only be an issue at higher temperatures where the device will slow down.
    As you can see, the propagation delays for the 65LVDS32 max out at 3ns, and the 55LVDS32 versions are 6ns. This added delay will likely add some additional component to the 1ns part to part skew max. Worst case I would estimate it could add 50%. This has same stipulation as commercial datasheet. Same package, temp, voltage, loading, ... Also, the higher the load, the more this could aggravate any differences between devices.
    Hope this helps.

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 40 points
    Hi,

    I'm the customer for which Anthony ask the question. I thank you for the answer but I need a complement information.
    I use on my design SN55LVDS33-SP and SN55LVDS32-SP on the same interface. I need to know if the part to part skew could be similar. The part to part skew on SN55LVDS33-SP is done on datasheet, it equals to 1.2ns. The part to part skew for the SN55LVDS32-SP is not provided.

    Does it exist a part to part skew for the reference SN55LVDS32-SP ? With your answer,I understand that we consider a part to part skew of 1.5ns in worst case

    Could I consider that the 2 devices belong to the same family and then the part to part skew is the same for all SN55LVDS3x-SP ?
    Could I use this specification item to compare the 2 devices that are present in the same interface (1 devices for the clock and the other for the datas) ?

    Best regards,

    Laurent
  • 0 in reply to Laurent CHAPEL
    TI__Guru 62930 points
    Laurent,
    I do believe the part to part skew between the two devices will be very similar.
    The commercial version of the LVDS32 shows a part to part skew of 1ns. I believe it would be reasonable to extend this to 1.5ns for the military version to accommodate the temperature extension. Unfortunately, this parameter is not specified, tested, or warranted.

    However, as you suggest they are from the same family and technology, and should have similar trends for parameters.

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 40 points

    Hi,

    Thank tou for your reply.

    But I need a complement information : I use the 2 parts (LVDS32 and LVDS33) on the same bus. These signals are adjust in length and then in timing.

    But the fact that the 2 devices have different references, I don't know if I can use the parameter "part to part skew". Indeed, the part to part skew is given for 2 LVDS32 or 2 LVDS33 but not for 1 LVDS32 and 1 LVDS33.

    Is it correct ? Could you give me some complement information about this parameter ?

    Best regards,

    Laurent

  • 0 in reply to Laurent CHAPEL
    Prodigy 40 points

    Hi,

    Could you help me ? Do you understand my trouble ?

    Best regards,

    Laurent

  • 0 in reply to Laurent CHAPEL
    TI__Guru 62930 points

    Laurent,

    I apologize for delay, as I have been out of the office.

    I now understand your concern.   The two devices have different propagation delays, so this will make their part to part skew be significantly different.

    For example the TPHL ranges from 1.8 to 8ns with typical of 4ns for the LVDS33.

    The same parameter for the LVDS32 is 1.3 to 6ns with typical of 2.3ns.   Based on typical values, this will introduce a shift of about 1.7ns without considering the part to part skew parameter.  The "new" part to part skew between devices could easily exceed 3ns.

    Regards,

    Wade