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TPS2375 N/C pin

Scott McClusky
Prodigy 30 points
Other Parts Discussed in Thread: TPS2375, TPS2376
Hello,
Where can the N/C pin on the TPS2375 be connected?
I do not want to leave this pin floating because during EMI susceptibility testing we have had this chip fail for unknown reasons.
Connecting N/C to the RTN pin breaks the chip.

Thanks,
Scott


  • 0
    TI__Mastermind 42795 points
    Hello Scott,
    I am confirming with the designer and will report back to you. My hunch is that connecting it to the VSS pin would be OK but I want to get confirmation from design first.
  • 0 in reply to Eric Wright
    TI__Mastermind 42795 points
    On the TPS2375, this pin is not internally connected to the die (no bond wire). Floating the pin should not have been an issue, but if it were subjected to a high voltage such as through ESD then an arc could have occurred. Connecting pin 7 to the VSS pin will at least put the pin at a known voltage level at all times.
  • 0 in reply to Eric Wright
    Prodigy 30 points
    Hi Eric,
    Thanks for the prompt and thorough reply.

    Interestingly, when I test three different chips with a Fluke 73 and Fluke 189 meter set to Diode test I get 0.63V and 0.67V, respectively, from pin 4 (positive lead) to pin 7 (negative lead). This is with the chip out of the circuit (not connected to anything). Perhaps the chips I have are a previous revision. The chips I'm testing are marked:
    2375
    [TI symbol] 29M
    A85KG4

    Could this be related to my problem?

    Regards,
    Scott
  • 0 in reply to Eric Wright
    Prodigy 30 points
    Hi Eric,

    The pin appears internally connected, based on directly measuring the chip.

    When I test three different chips with a Fluke 73 and Fluke 189 meter set to Diode test I get 0.63V and 0.67V, respectively, from pin 4 (positive lead of DMM) to pin 7 (negative lead of DMM). This indicates an internal connection, such as an ESD diode, connected from pin 4 to pin 7. See my previous post for the chip markings.

    Thanks,
    Scott
  • 0 in reply to Scott McClusky
    TI__Mastermind 42795 points
    Hi Scott,
    My earlier reply regarding the abscence of the bond wire from the pin to the die was incorrect. As it turns out, the bond wire is connected and there is an ESD structure from pin 7 to pin 4 as you've measured. I apologize for the wrong information.
    The TPS2376 thru a metal mask change simply connects the ESD structure terminated pad from pin 7 to the internal UVLO comparator. The pin rating is 10V maximum for TPS2375,6,7 so it makes sense that connecting this to the RTN pin would cause damage. We feel that connecting pin 7 to pin 4 (VSS) is still the safest option and we will update the datasheet to reflect this information.
  • 0 in reply to Eric Wright
    Prodigy 30 points
    Hi Eric,
    Thanks for clarifying this. We will proceed with this pin connected to VSS. We appreciate your help.
    Regards,
    Scott