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DS90LV001TM distorting signal

David R Rowley Jr
Prodigy 20 points

basicly, i have one DS90LV001TM/NOPB driving another '001. when last device is enabled, signal becomes distorted and distorts thru entire data path; not just the line being driven. Source/load: channel link @ 25Mhz input... BTW: group 5+c works fine, distortion only occurs on other two groups. Removing one driver, like B and single (A) '001 driving the other '001, still fails.  'T' is 100ohm termination.

  • 0
    TI__Mastermind 43795 points

    I would look at the waveforms at each input and output in groups 1/2 and 3/4.  Having a 25 MHz source clock requires a 300 Mbps data-rate.  Multi-drop connections like those of LV001 A +B or LV001 a+b+c could have stub lengths long enough to distort the signal.

    The enabling an LV001 device should not impact the signal at its input.  It sounds like you have looked into contention between LV001 devices, but could it be possible that two LV001's are driving the same net?  How far apart are LV001 "A" and LV001 "B" ?  How far apart are LV001 "C" and LV001 "D" ? 

    Is the power and ground distribution done with planes?

    Do the connectors also carry power and ground ?

     

  • 0 in reply to Lee Sledjeski
    Prodigy 20 points

    thanks for the reply.

     

    turns out, bad scope bandwith and bad assumptions.

    the assumption was, i was told the source side of the was working properly, it was not. the source was outputing all zero's to the serializer, (suppose to be x01F, sync signal).

    if i had a better scope, i would have seen that the signal was 1 bit in length or the stop bit.

    i violated all my normal debug technics, assume nothing and i new the scope bandwith was not wide enough. Just a bad week when alot of things weren't working.

    devices work fine. but did find, other than a couple, you can't use them in multidrop mode.