• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 205 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.

LM5121: technology discussion

Cooper Zhang1
Expert 2190 points
Part Number: LM5121

hi ,

Boost IC LM5121MHX，CTM replaces Mos （Q6，Q7,Q8）,but the work is not normal , we tried to delay soft startup time by adding C52 capacitance, it is ok；

I want to know what is the impact on the C52 value ？

SCH & the test result waveform and MOS PN as below

新旧MOS管测试对比总结报告 -20220830.xlsx

  • 0
    TI__Genius 16985 points

    Hello Cooper,

    Thanks for reaching out to us via e2e.

    I cannot read the Chinese comments inside the Excel sheet.

    Can you please explain in more detail what your question exactly is?
    And which parts of the diagrams (point of time) you are referring to?

    Some questions:
    I would understand that the purple curves are VOUT.
    Are the blue curves VIN? Or something different?
    Is the battery so weak that the voltage drops as soon as the output capacitors get charged?
    Which load was connected when these oscilloscope screenshots were taken?

    Thanks and regards,
    Harry

  • 0 in reply to Harry Hofner
    Expert 2190 points

    Hi Harry：

    Q1：For LM5121 boost ic， I want to know what is the effect on the C52 value ？

    Q2:  after  I replaced  Q6 & Q7 & Q8 from  LTS0111SR to VBE1101N，the power is not ok,  I need add the C52 capacity to delay the soft start up time , the power is ok , why ?

  • 0 in reply to Cooper Zhang1
    TI__Genius 16985 points

    Hello Cooper,

    > what is the effect on the C52 value?
    The bigger the softstart capacitor is, the slower and more flat will be the ramp when the converter starts booting.
    It should not have any other effect.

    > the power is not ok
    I do not have enough information. What exactly does "not ok" mean?

    This voltage drop in the blue line shows that your supply for the input power is too weak to deliver the necessary current. When you slow down the ramp, less current is necessary, so you don't see that drop.

    Best regards,
    Harry

  • 0 in reply to Harry Hofner
    TI__Genius 16985 points

    Hello Cooper,

    I have not heard from you for more than two weeks, so I am closing this thread now.
    Please open a new one in case of additional questions.

    Best regards,
    Harry