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LP8860-Q1: Shortcut on Vdd

Dieter Heinrich
Prodigy 20 points
Part Number: LP8860-Q1

Hello,


I have a problem with the LP8860.

Sometimes the circuit with the LP8860 provides a short circuit for the voltage supply immediately after switching on.

The voltage then breaks from 24VDC to about 3VDC.

Often, the fault has disappeared again after a new voltage is switched on, so the LP8860 works properly.

Now I have the problem that the LP8860 permanently forms a short circuit between Vdd and ground (the connection Vdd to the rest of the circuit is separated).

Obviously the chip is defective.

How can the problem occur and how can I prevent it in the future?

Thank you

Dieter

  • 0
    TI__Intellectual 2140 points
    Hi,

    There may have been a short somewhere in the circuit that caused this. We will assign an engineer to this thread to assist you. You will be asked to provide some additional information to assist the debugging process.

    Regards,
    Angelos Tsiros
  • 0 in reply to Angelos Tsiros
    Prodigy 20 points
    Hello,

    Thank you for your reply. I have looked at the circuit diagram page 17 in the user guide LP8860-Q1EVM Evaluation Module (SNVU382A) again. There is a resistor R23 with 0Ω from PGND to GND. What happens if this connection is missing.

    Thank you
    Dieter
  • 0
    TI__Intellectual 1235 points
    Hello Dieter,

    It seems that a potential PCB layout issue may be causing the issue. Could you please provide the application details and test conditions that led to (i) the intermittent and (ii) permanent short failure?
    Could you please check the continuity of your circuit that failed the short in the following two scenarios?
    (i) By measuring continuity using the PCB that has already failed (after removing LP8860 from the PCB)
    (ii) By measuring continuity using a brand new PCB (without LP8860 mounted on PCB)
    (iii) By measuring continuity using a brand new PCB (with LP8860 mounted on PCB)

    Kind Regards,

    David
  • 0 in reply to Dieter Heinrich
    TI__Intellectual 1235 points
    Hi Dieter,

    Sorry I missed the post with your question regarding R23. For some reason I didn't receive a notification associated to such post.

    Well, R23 is basically a net tie (GND - PGND) and I don't see how missing that connection would impact the shorting scheme. I don't think that missing that connection would cause the short issue you're seeing.

    By the way what are the test conditions you are using?

    Kind Regards,

    David