• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 253 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.

LMZ31530: Schematic Review

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: LMZ31530

Dear Team,

Do you have further comments for this design?

BR

Kevin

  • 0
    TI__Mastermind 47060 points

    Hi Kevin,

    Other then the questions/comments I listed below, everything else looks okay:

    1. Is this an evaluation schematic? From the looks of the FREQ_SEL configuration the 0Ohms resistor (R31 and R34) look like placeholders for different frequency selection. It is recommended to have a switching frequency of 500kHz following Section 8.2 of the datasheet. This is achieved by floating the FREQ_SEL pin. Since the application is for 0.88V output, the highest switching frequency that I would recommend is 650kHz. 
    2. The VADJ resistor combination is roughly 2940Ohms and will be close to 0.9V output. I would recommend increasing the value if you want 0.88V output. Perhaps you can pick 3.05kOhm resistor which is available in 0.1% tolerance. This will help keep the output voltage close to 0.88V. 
    3. Lastly, what is the use of R26/R27/R29/R30? Are these load resistors?

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Genius 9710 points

    1.Change R31 from NC to 715 ohm + 30 ohm (add one resistor)

     

    2.Change resistance combination to be close 3.05Kohm for 1Kohm + 1Kohm + 523ohm + 523ohm (3.046Kohm)

     

    3.It’s original design by customer on 1.0v, I think its’ function should be discharge resistor.

     

    4.In addition, Is IHN voltage a 4.7v and high enable?

  • 0 in reply to Kuan Wei Chen (Kevin Chen)
    TI__Mastermind 47060 points

    Hi Kevin,

    This clears up a few of my concerns with the schematic. Sounds like the application will be at 650kHz which is the maximum switching frequency that will enable 0.88V output rail.

    The INH pin is high enable that requires a minimum of 1.8V to be above the INH high voltage threshold if the INH feature is desired. Otherwise, the INH pin may be left floating and the internal pull up source will automatically enable the part.

    Regards,

    Jimmy