• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 2277 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.

LM5116: LM5145- Using Synchronous Buck DC-DC Controller design variable/Programmable wide rage Vout

Sachin Dighe
Prodigy 70 points
Part Number: LM5116
Other Parts Discussed in Thread: LM5145, , PMP7282, PMP20178, LM5146

Hi, 

Requirement of DC-DC Buck Converter 

Vin = 48Vdc

Vout min = 5Vdc

Vout max = 40Vdc

Iout min  = 0.5A

Iout max = 30A

I wanted to design programmable DC-DC buck converter using LM5116/LM5145 whose output voltage changes by changing the feedback pin voltage using DAC. 

All the design calculation in datasheet of LM5116/ LM5145 are considering fixed output voltage.

The webench design can not be used for wide range output voltage (such as  5VDC to 40VDC). 

Please guide how to design the programmable DC-DC buck converter using LM5116/LM5145 for above listed requirement 

Also I have checked the reference design http://www.ti.com/tool/PMP7282 

 

  • 0
    TI__Mastermind 25590 points
    Sachin,

    PMP7282 is a great resource. It's definitely a good place to start.

    I recommend designing for a fixed 24V or 30V output, create a robust design, then simulate for your edge cases (VOUT = 5V, VOUT = 40V). You can simulate using WEBENCH or TINA/Spice. You may run into an issue trying to simulate 30A since WEBENCH only allows 20A on LM5116 but you can simulate for half the load if you're going to utilize the interleaved approach of PMP7282.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 70 points
    Dear Sam,

    Thank you for your quick response.

    I am not going to have interleaved approach of PMP7282 instead I will be having single chip meeting required output.

    The limitation I have is simulating for edge condition at required load (Iout). I don't want to go with trial an error method as I have limited time.
    Will you be able to suggest modification required in PMP7282 so that I can try out ?

    Regards,
    -Sachin
  • 0 in reply to Sachin Dighe
    TI__Mastermind 25590 points

    Sachin,

    This spec may be difficult to meet with a single-phase solution. But if this is a requirement I'd recommend starting by looking at PMP20178 and scaling up the inductor and FETs. You can check the rise-times and fall-times of the FETs with the current capability in the LM5145 datasheet and if LM5145 is not sufficient, you can check out our gate drivers to assist.

    -Sam

  • 0 in reply to Samuel Jaffe
    Prodigy 70 points

    Dear Sam,

    If design and development of single-phase solution is difficult and has larger risk in terms of performance then we can think of two phase solution (similar to PMP7282). There is no harsh requirement of single phase solution.

    If I am not wrong the two phase solution will equally split output power requirement in two phase which will be connected in parallel to achieve desired output power?

    I have tried LM5116 and LM5146 WEBENCH design (Please check the attachment). Input and Output parameter for both design are same.

    Vin min = 46V, Vin max = 50V

    Vout = 24V, Iout = 15A

    Tamb = 40DegC.

     

    1. Which design LM5116 or LM5145 you will recommend considering two phase approach?
    2. Again the challenge here is output voltage range 5V to 40V. Can you help to tweak the design (LM5116 or LM5145 which you feel appropriate for my requirement) to obtained output voltage range 5V to 40V?
      1. For Your Information - For output voltage 24V and above if output current drops below 15A will also be fine/acceptable because at higher output voltage the output current requirement is less.LM5145RGYR_44.0V-50.0V to 24.00V @ 15.0A.pdfLM5116MHX_NOPB 46.0V-50.0V to 24.00V @ 15.0A.pdf

  • 0 in reply to Sachin Dighe
    TI__Mastermind 25590 points
    Sachin,

    Yes, 2 phase should split the power evenly so each phase delivers half the power.

    1. I think both should work but I'd recommend LM5116 so that you have PMP7282 as a reference.
    2. I went into WEBENCH and it's easier to design for 5VOUT, then check for higher VOUTs. Change the top feedback resistor to get the desired output voltage and check the compensation. Align with the datasheet to make sure L, CIN, and COUT are still acceptable for those specs.

    -Sam
  • 0 in reply to Samuel Jaffe
    Prodigy 70 points

    Dear Sam,

    I was trying to simulate the PMP7282 single phase in TINA but it is not working as expected. The output Vout drops below 10V for Iout 25A. Also the output ripple and inductor current overshoot and undershoot are very high.

    I configured Vin= 48V and Output Vout =12V Iout=25A

    Can you help me to adjust some simulation parameter of the design. Please find attached TINA design file.

    Regards,

    Sachin Dighe

    snvm051b - autosave 18-08-17 16_58.TSC

  • 0 in reply to Sachin Dighe
    TI__Guru 74052 points
    Hi Sachin,

    Please review and complete the quickstart calculator available by download from the product folder.

    Regards,
    Tim
  • 0 in reply to Timothy Hegarty
    Prodigy 70 points

    Dear TIm,

    I got the LM5116 design working for 12V, 20A with single MOSFET (BSC037N08NS5ATMA1 - Infineon Technologies). Please find the attachement

    Request you to provide your valuable input on making it suitable for output range 5 to 40V, specifically on inductor, compensation network.

    LM5116_12V_20A_Design.TSC