• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 321 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LM51551: LM51551

Ian Wang
Mastermind 29770 points
Part Number: LM51551
Other Parts Discussed in Thread: LM5155

Hi Sir,

What if LM51551 not have FB voltage? device will lock or burn out?

If lock, how to un-lock?

Thanks, Ian.

  • 0
    TI__Guru* 78440 points

    Hi Ian,

    If there is no voltage at FB pin, the circuit will become open loop and it may run at the max duty cycle.   Depending on the actual situation, the current limit achieved by the CS pin may or may not catch the failure in the FB pin. If it can catch, the circuit can enter the hiccup mode, but if not, excessive output voltage can be produced which may cause damage.

    To mitigate the failure, you may consider to put parallel resistors for the high side of the FB resistor divider to cover the failure of single resistor open. 

    Thanks,

    Youhao Xi, Applications Engineering

  • 0
    TI__Mastermind 21720 points

    Hi Ian,

    Thanks for reaching out with your question and for considering the LM5155 in your design.

    Are you asking what will happen if the FB pin is connected to 0V?

    In that case the LM51551 will run into peak current limit and then hiccup mode will be triggered. This will happen continually until FB is not shorted to ground.

    Please let me know if you have any questions.

    Thanks,

    Garrett