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SN65HVD1176: Part-to-Part propagation time variance

Evan Ford
Prodigy 10 points
Part Number: SN65HVD1176

Assuming the exact same input was driving infinite SN65HVD1176 RS-485 transceivers, and the single-ended input went from 0 to 3.3v, if measuring the output of each driver on a scope what would be the maximum time between the first and last transition on the output?

I need to understand the part-to-part propagation time variance, given identical inputs, to verify if I can meet strict timing requirements with this part.

Thank you

  • 0
    TI__Guru 74252 points

    Evan,

    An engineer has been notified of this post and will respond by the end of day tomorrow. Thank you for your patience.

    Regards,

    Eric Hackett 

  • 0
    TI__Guru 52172 points

    Hi Evan,

    The official answer is 6ns - but that is unlikely and assuming that both max and min times have been hit in the same line of parts (which isn't realistic as temperature is going to affect that much greater).

    However that being said we don't have a statistically significant spec to give besides the 6ns as that is the max (10ns) - the min (4ns). In reality it depends on the system setup of the parts - at 25C there isn't going to be much variation between parts - probably around 1.5ns - 2ns max and typical it would probably be less than 1ns. If the devices are in a colder environment all the parts most likely will be running closer to the 4ns region and if at max temp closer to the 10ns but both these regions could possibly have more spread between devices. This is all assuming a 54 Ohm + 50pF capacitor in parallel for the loading - so if there is higher C it could really increase the output times and any small variation could be magnified if this isn't the case

    What timing spec are you trying to hit for this application?

    Do you know the ambient temperature range that the application?

    Do you know how the RS-485 bus will be loaded in the application ? 

    . 

    Please let me know because if I have this information I may be able to give you a better educated guess that is lower than 6ns - but the 6ns is what we would guarantee (under the tested conditions - which may be slightly different that your system)

    Best,

    Parker Dodson