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Original question:

DS90UB928Q-Q1: Problem of Serial Link Fault Detect

DS90UB928Q-Q1: DS90UB928Q-Q1

nabil saidoun
Prodigy 110 points
Part Number: DS90UB928Q-Q1

Tool/software:

Hello 

Please share with us a technical note detailing the TI DESER 928 limitation to detect below Lanes faults in order to discuss the impact with our customer (SoC Serializer TI 943)

RIN+ short to RIN-:

RIN+ short to GND:

RIN- short to GND:

RIN+ short to U3V3:

RIN- short to U3V3:

  • 0 in reply to nabil saidoun
    TI__Mastermind 33485 points

    Hi Nabil,

    Line-fault limitations on the 928 are as follows:

    • Line-faults can only be detected on the 928 through the lock detection bit
    • This bit can not differentiate between different types of faults

    For detecting shorts to battery, any component that can be compromised by the battery voltage (i.e. 12v), needs to be accounted for. ESD diodes can be moved to the IC side of AC caps to prevent shorting.

    For a 943A->928 system, line-fault is recommended to be implemented on the 943A since it has a built-in ADC and is adjacent to the system controller. There is an app note for FPD-Link IV line-fault but I cannot send it here.

    Best,

    Jack

  • 0 in reply to Jack Scherlag
    Prodigy 110 points

    Hi Jack

    This option to do it via read out of remote register at serializer side is not possible as the Back channel is closed

    As said lock detection bit is not updated when the conditions #2 till conditions #6 as per chapter $8.3.12 are applied. Please refer to original question

    e2e.ti.com/.../ds90ub928q-q1-problem-of-serial-link-fault-detect

  • 0 in reply to nabil saidoun
    TI__Mastermind 33485 points

    Hi Nabil,

    The UB928 is limited in its fault detection capability. It relies on the link becoming compromised and losing lock. Not all cable faults (i.e., short to a DC bias) will necessarily result in a link where the UB928 can recover lock.

    In a system with a SoC->943A->928, we can implement a full line-fault feature on the 943A side of the link. There is internal hardware that will measure the DC level on the cable. This hardware is not available on the 928.

    Best,

    Jack