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LM51770EVM-HV: LM51770EVM-HV

Leo Tabakin
Prodigy 10 points
Part Number: LM51770EVM-HV
Other Parts Discussed in Thread: LM51770

Tool/software:

Can LM51770EVM-HV be used to boost from 24V input to 48V output? If the answer is yes, what changes have to be made to the board, besides, maybe, the compensation network?

If an application requires boost from 24V input to output voltages from 26V to 52V, what is the best method to calculate compensation network?

  • 0
    TI__Intellectual 1380 points

    Hi Leo,

    Thanks for using E2E! You could use the calculation tools to get a reference compensation parameter. Also attach the EVM user guide for you reference. Thanks. 

     LM51770-QUICKSTART-CALC Calculation tool | TI.com

    LM51770 Buck-Boost Controller High Voltage Evaluation Module

  • 0 in reply to Alicia Hao
    Prodigy 10 points

    Hi Alicia,

    Thank you for prompt reply, however you didn't answer any of my questions. 

    I'll try to rephrase them:

    1. LM51770EVM-HV spec: input voltage ranges from 36V to 48V, regulated output 48V.

    Question: Will LM51770EVM-HV work if input changes to 24V?

    Sure, I may need to recalculate the compensation parameters and UVLO seems should be in the range as is.

    2. I'm designing voltage regulator with LM51770. Spec: Input 24V, Output adjustable from 26V to 52V. QuickStart calc compensation parameters for example:

    26V output - Rcomp = 221K, Ccomp = 8.2nF, Chf = 0.82pF

    52V output - Rcomp = 150K, Ccomp = 8.2nF, Chf = 0pF

    Question: How to choose the compensation parameters that will work for full range of output voltages?

    3. And here is additional question:

    Buck-boost LM51770 regulator design, input 24V and output ranges from 5V to 52V:

    Question: What is the best approach to selecting adequate inductor and compensation parameters from the variety recommended by the QuickStart spreadsheet and WEBENCH Designer tool for different output voltages ranges from 5V to 52V?

  • 0 in reply to Leo Tabakin
    TI__Intellectual 1380 points

    Hi Leo,

    Please give me some time to look into this, thank you. 

  • +1 in reply to Alicia Hao
    TI__Intellectual 1380 points

    Hi Leo,

    1) In boost mode you may need to check what's the maximum input current in your application when Vin min is 24V and set current limit appropriately.

    2) and 3) are quite similar. Recommendation parameters showing in Quick calculation tools are usually good starting point but not the only appropriate compensation work. You could start with them and see if the system performance is still acceptable with Vout change.