• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 445 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.

LP2951: unable to obtain fixed 3.3V output voltage

Tulsi Chowdhury
Prodigy 20 points
Part Number: LP2951

I am using LP2951, with fixed output voltage as 3.3 V. the input is 14.4V and i have connected the out and sense pin together. also thefdback and vtap pins are connected together to obtain a fixed output voltage. however i am measuring an output voltage between 1.05-1.15V, and it is not fixed and fluctuates within this range.  I have attached a schematic diagram for reference. please tell me how can i obtain a fixed output voltage of 3.3v

  • 0
    TI__Mastermind 43610 points

    Hi Tulsi,

    The schematic you have is trying to override the fixed output setting. 

    For a fixed ouptut, removing R53002 and R53003 will do the job.

    For adjustable output, the connection between OUT and Sense and VTAP and FDBACK must be broken. Here is the schematic from the EVM guide:

    It then describes the following:

    Another concern in going from 14.4V to 3.3V is a big voltage drop and it is possible you are seeing the effects of thermal shutdown. If you are using a multimeter, it averages out the voltage and may look like an unstable lower voltage. If you use an oscilloscope you might see the thermal oscillation more clearly.

    I hope this helps.

    Regards,

  • 0 in reply to JCHK
    Prodigy 20 points

    Thank you for the answer. It makes sense and will solve the issue hopefully.

    Cheers