• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 498 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM46002 over voltage protection and failure mode

Paul Schoenke
Expert 1375 points
Other Parts Discussed in Thread: LM46002

Hello E2E forum!

I am looking for additional information on the LM46002 which I am not able to find.

1. I know from experience that the feedback path with the resistor divider can cause problems, especially if a technician decides to probe that net...the output will take a big step (not good).  What I am looking for there is some scheme for output over-voltage protection.  I plan to use smaller value resistors to help minimize the issue with technician probing on the board.  But, if there is a short from the feedback pin to the common, then the input voltage might show up at the output.

 2. What happens if the LM46002 fails?  I mean, if it were to fail will it fail open or short?

 My biggest concern with any DC-DC converter is protection of loads at the output.  If there are simple things I can do to prevent this event, it seems prudent to do so.

Any feedback or input is welcomed and appreciated!

Thanks again!

Paul

  • 0
    TI__Genius 16025 points
    We've received your query and will get back to you shortly.

    Thanks,
    Anston
  • 0 in reply to Anston Lobo
    TI__Genius 11085 points

    Paul,

    The LM46002 does not have an over voltage protection. In case of over voltage. the IC will stop switching and depends on the load to ramp down the output voltage. In case of FB node short to ground, Vin level will be seen at Vout. Since the only information the IC has for the Vout is through FB node, it has no protection under this condition. To protect the load in this case, you can add a zener diode from Vout to ground to clamp the exess voltage. The zener voltage should be above the regulation voltage and below the abs max input voltage of the load.

    The other concern when Vout=Vin is the abs max voltage on Bias pin of the LM46002. If Vout is >=3.3V, it will improve efficiency if Bias pin is tied to Vout. But if Vin is above 30V, Bias pin can be damaged when Vout = Vin.

    If Vout or load has an over current or short circuit event, the LM46002 has hiccup mode to protect itself and the load from over heating. It retries and restarts normally after the OC or SC condition no longer exist.

    In terms of how the LM46002 fails, do you mean what happens when the IC is damaged? Then it depends on which part of the IC is damaged.

    Hope it helps.

    Yang