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DS26LV32

Sean Chen99149
Prodigy 10 points
Other Parts Discussed in Thread: AM26LV32E

Recently, we found the batch 2M06RF chips DS26LV32 serious latch-up. As long as the differential input with a negative 1 volt voltage, the DS26LV32 immediately intense heat. Any one also found this situation?

  • 0
    TI__Expert 5175 points

    Greetings -

    This is a RS422 Receiver, there are two types of inputs (LVCMOS, the enables) and RS-422 inputs (4 channels, 8 inputs).  The RS-422 inputs are specified to take +10V to -10V input levels and adhere to the RS-422 input current specification.  These inputs are very robust, I do not expect them to be the problem.

    The LVCMOS inputs are logic inputs and are designed to be switched from rail-to-rail only  (Gnd to VCC).  ABS MAX is specified as -500mV to (Vcc + 500mV).  I am concerened that your reported input undershoot exceeds the ABS MAX rating by 2X.  I suspect the excessive undershoot is causing the problem.  You also reported intense heat, this can be due to a false triggering of the ESD protection path that causes an internal VCC to GND shunt to turn on (used for ESD protection).  This if occuring it is causing high current to flow and the resulting heat. 

    I would suggest to filter or slow down (if programable drive strength) the edge to remove the undershoot.  As if this was the failure mechanism it should now be prevented.  Exceeding the ABS MAX on this device is not recommended.

    If you are unable to alter the undershoot, TI offers two different 3.3V RS422 receivers now (TI & National), the other device utilizes a different ESD scheme and process, it may be more tolerant to exceeding the undershoot abs max - see AM26LV32E

    To a speedy resolution.......

    John Goldie
    DPS APPS / SVA

  • 0 in reply to John Goldie
    TI__Expert 5175 points

    Greetings -

    I just  re-read your post, and applying -1V to a RS422 input is not expected to cause a problem.  The RS-422 input impedance is 4k ohm min and a sweep of the input from -10 to +10 is expected to show that or higher impedance.  Also, we do not have other reports of a problem to date.  The part is rather robust.  Please do ensure GND is applied when applying an input voltage also.  

    John Goldie
    DPS APPS / SVA