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Newer DS90UB901QSQE & DS90UB902QSQE not working so well.

Eric Strohbehn
Intellectual 360 points

Hi TI support person,

We have been experiencing a reduced level of performance with the DS90UB901QSQE & DS90UB902QSQE chips we purchased recently.  Here is the marking information from the top of the chips:

Good UB901SQ  has date code:  VM17AB

Bad UB901SQ  has date code:  VM26AB

Good UB902QSQ  has date code:  VM17ABE3

Bad UB902QSQ  has date code:  VM19ABE3

Has there been any change in the way the equalization or power output of the serializer gets produced?

Thanks,

Eric Strohbehn

  • 0
    TI__Expert 5210 points

    Hello Eric,


    Can you please clarify on the issues being seen regarding the "reduced level of performance"? Does this mean that with the "bad" chips, the customer is losing LOCK? Any issues that the customer is seeing would be helpful to know for debugging purposes.


    -Sean

  • 0 in reply to Sean Thornton1
    Intellectual 360 points

    Hi Sean,

    We don't lose lock but rather pick-up CRC errors.

    I am focusing on the UB902QSQ since we have a 2nd instance where the date code VM19ABE3 is not working.  In this case the I2C locks up.  It would help us to be able to decipher the date code.  Can you tell us what the following codes mean?

    VM19EBE3         

    VM17ABE3         

    VM21ABE3       

    Thanks,

    Eric

     

  • 0 in reply to Eric Strohbehn
    TI__Expert 5210 points

    Hello Eric,

    I have looked up all of the codes you listed for 901 and 902 devices and none of these lots have had issues after production.

    By stating above that you are having CRC errors, I am assuming you are seeing issues with I2C transmission on the back-channel. If this is the case, please make sure that your PCB traces on DOUT+/- and RIN+/- are 50 Ohms AC impedance per trace (100 Ohms differential). Typically we recommend an 8 mil trace width and a 1.30 mil GND fill below this. Also be sure that the traces are routed close together, are as short as possible, aren't routed through vias before the connectors (i.e. this introduces impedance discontinuities which can cause reflections), and are length-matched from chip to connector on the PCB.

    -Sean