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DS90LT012AQ / DS90LV011AQ Overstress

We have two circuit cards that use several DS90LT012AQ and DS90LV011AQ LVDS interfaces to communicate between each other.  Both discrete signals and serial communication is transmitted with these LVDS interfaces. Each circuit card has it's own 3.3 V supply derived from a shared 15 V supply.  If one circuit card were to have it's 3.3 V supply go over-voltage, possibly to the 15 V rail, what damage to the interfaces can we expect?  I see the absolute maximum supply rating of these devices is 4.0 V from their datasheets.

If the DS90LV011AQ driver experienced an over-voltage on it's supply, would it transmit a damaging voltage to the corresponding DS90LT012AQ receiver?

Would the receiver be damaged such that it could draw excessive current from the still health 3.3 V supply?  

Would the receiver be damaged such that it could deliver a damaging transient to the healthy 3.3 V supply or down stream circuits on the healthy circuit card?

I do not expect a receiver that has been exposed to an over voltage condition on its supply to cause damage to a driver on the healthy circuit card / supply. 

Are either of these devices prone to Latch-up when the absolute maximum ratings are exceeded?

Additionally, will a receiver on the circuit card with the over-voltage condition have an output at the supply rail, ground or indeterminate?

Thanks,

Jesse

  • Hi Jesse,My apology to getting you a late reply.
    From the description, it appears you are concerned about over-voltage applied to the driver, and the subsequent fault to the receiver and its power regulator.
    When you apply an over-voltage to the VDD pin beyond its max absolute rating, I expect it may cause a voltage breakdown, it is hard to predict if it may cause an open or short condition to other pins of the device. When an over-voltage is applied to an input pin of the receiver, the likely scenario is that it will turn on the ESD protection circuit at the input pins, which produces a current path from the input pin to the VDD pin.
    I highly recommend to avoid over-voltage and find way to keep it to the safe operating voltage range. One option is to put a zenor clamping diode at the VDD pin to keep it at a safe voltage even there is a fault condition at the regulator.
    regards,TK Chin
  • Hi TK Chin,

    This is for a failure mode analysis. If we assume the damaged driver output fails shorted to the overvoltage supply, then your description of the current path through the ESD diode from the receiver input pin to VDD leads me to believe that the healthy supply may in turn experience a transient overvoltage condition ( at least until the ESD diode or other current carrying path is damaged). This confirms the worst case scenario that an overvoltage condition on one supply may propagate across the LVDS interface and impact a healthy supply rail.

    Thanks,

    Jesse