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DS90UB913/914 signal measurement

David Park
Expert 6630 points

Hi,

Could you explain about signal measurement of DS90UB913/914?

I recommended using BERT but customer wants to see the signal on an oscilloscope.

In the datasheet, there is below picture.

When customer measure the signal on their oscilloscope, they could see below signal.

Is this normal signal? 

  • 0
    TI__Genius 13475 points
    The FPD signal consists of a forward channel and a backchannel signal, superimposed on one another, so if you try to look at the signal on a scope, you will not get a clean eye diagram. The best way to observe the signal is with the CMLOUT function on the DS90UB914 - the input to the '914 has a circuit which separates the forward channel from the backchannel, and the recovered forward channel can be buffered and routed to the CMLOUT pins on the device before the signal is sent to the CDR circuit which will clean it up and extract the clock and data information. The CMLOUT function is described in the DS90UB914A datasheet. The pins for the CMLOUT function are brought out to SMA connectors on the DS90UB914AEVM which makes it easy to connect to an oscilloscope.