• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 230 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.

Need clarification on TPS56121

jeyalakshmi kanniah
Prodigy 60 points
Other Parts Discussed in Thread: TPS56121

     I am using the TPS56121 part in my design with the following requirement.

 

Requirement:

               Vin(min) – 11V

               Vin(typ) – 13V

              Vin(max) – 13V

               Vout – 1V

              Iout(max) – 9.5A

                     I am using the switcherpro tool for designing the circuit. In that the inductor value is 1uH. If I am calculating the inductor value by using the formula given in the datasheet(Page-16), I am getting 64.7nH value. Which value I have to use. Please provide the guidelines to finalize the value .

  • 0
    Mastermind 7395 points

    I checked the formulas in the datasheet and for the example there, the inductor should be 41.3nF and not 413nF as stated. A x10 factor is missing somewhere and maybe it explains the difference between your calculations and the switcherpro results.

  • 0 in reply to Avi Chami1
    Prodigy 60 points

    The inductor value 41.3nF is not for my requirement. As per my requirement, the calculated value is 64.7nH and the switcherpro output is 1uH. can anyone provide the solution.

  • 0 in reply to jeyalakshmi kanniah
    Intellectual 450 points

    I think, you should get 647 nF as per data sheet equation.. looks like mistake of factor x 10 in your calculation.I calculated using the parameters you posted above & it comes 647nF. [ L = {(13-1)/(0.3*9.5)} * {1/13} * {1/(500*1000)} ].

    Regarding, selection of the inductance value in switcherPro, I believe tool might be selecting from the all inductors it has in database and 1uH might be closest and optimum choice (considering its ripple current, sat current & may be dcr ) .Tool might be evaluating the efficiency and other parameters (like GM, PM) and it might have found that 1uH is best option. Have you checked all other resistor & capacitor calculated through SwithcerPro is exactly matching to theoretical datasheet calculations ?

    If I have to design the same thing, I would go with SwitcherPro design.

    Thanks,

    Rizwan Hirani

  • 0 in reply to Rizwan Hirani
    Prodigy 60 points

    Thanks for your reply. Its useful for me