• State Resolved
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 41 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

LM5164: Input Capacitor and Output Capacitor Webench Suggestions

Keith Keller
Expert 6610 points
Part Number: LM5164

Tool/software:

Hello,

We're designing with the LM5164 and getting mixed messages from the Datasheet and Webench.

For input capacitor, webench is showing 2.2uF.  However when we "choose alternative" it shows a solution with only 0.39uF effective capacitance. (2 images below)

For output capacitor, webench is showing 10uF, but alternative solution shows something as low as 1.1uF effective capacitance. (image below)

>>>>> input capacitor >>>>>>

>>>>> output capacitor >>>>>

Thank you, Keith

  • 0
    TI__Mastermind 31380 points

    Hello Keith,

    Its quite possible that the input can output capccitors can low.  CIN needs to withstand RMS ripple currents and with a small capacitnce value the input ripple voltage will be a large ripple voltage.

    the output capacitor will detemine the ripple voltage and transinet perfromance is not as cricitcal for stability as the fixed frequecny control schemes...  I would keep with the recomended values and not pick the lowest values even though it may be feasible.

    Hope this helps.

    David.

  • 0 in reply to David Baba
    TI__Expert 6610 points

    Hi David,

    Ok so you're saying that there is not a minimum requirement for Cin and Cout on the LM5164.

    What we need to look at is input cap ripple, and output cap ripple and load-step transient response to determine stability, correct?

    Thank you, Keith

  • 0 in reply to Keith Keller
    TI__Mastermind 31380 points

    Keith,

    There is a minimum depending on the specification requirement.  The minimum is dictated by RM ripple currents and Vin ripple requirements for CIN and Stability, ripple voltage and voltage perturbation requirements for a load step transient for COUT.

    WEBENCH is given you these absolute minimums, Ceramic deratings and bench results will govern.  Suggest using the recommended values and go from there.

    Hope this makes sense.

    David.