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LM5177: For 1000W design

Jeff YANG
Mastermind 7795 points
Part Number: LM5177
Other Parts Discussed in Thread: CD4015B, LMK01801, LMK6C

Tool/software:

Hi,

Does TI have buck-boost controller can support for below design? thanks!

Vin : 10-50V

Vout : 12V

Pout 1000W

Thanks!

Jeff

  • 0
    Mastermind 7795 points

    Hi,

    I find LM5177 can using Parallel (Multiphase) Operation, but may I know the maximum parallel limitation?

    How many LM5177 can parallel whit each others? Is possible to parallel 4 LM5177 to support 1000W(83A)?

    thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Prodigy 550 points

    Hi Jeff,

    Thanks for using E2E.

    In theory there should be no limit on the number of LM5177s put in parallel as long as there is good connection between the COMP,SS/ATRACK and FB pins of each phase. Please refer to this app note for more information of the parallel operation: Parallel Operation of the Buck-Boost Converters Using LM5177 Buck-Boost Controller (Rev. A)

    It is possible to use 4 LM5177 to support 1kW. For less ripple, you can use an external clock with 90 degree phase shift for 4 phases. I will involve the clock team to suggest a device for that.

    Best regards

    Yezi

  • 0 in reply to Yezi Yang
    Mastermind 7795 points

    Hi Yezi,

    Thanks for your feedback, it is good news!

    Is there have LM5177 4 phase reference design can share to us?

    Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Prodigy 550 points

    Hi Jeff,

    We do not have a 4 phase reference design yet, currently only the parallel operation app note is available.

    Best regards

    Yezi

  • 0 in reply to Yezi Yang
    Mastermind 7795 points

    Hi Yezi,

    Got it, and how about the external clock suggestion?

    Should we keep using CD4015B or other better suggestion?

    Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    Mastermind 7795 points

    Hi Yezi,

    For the 4 x external N-MOS, would you also suggest suitable part to us?

    Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Prodigy 550 points

    Hi Jeff,

    The MOSFET used in our EVM is not suitable for your case. I'm not a MOSFET expert, but hopefully I can give you some suggestions about selecting the right part.

    You can use our Power Stage Designer tool to find the max ratings of the MOSFET in your design: POWERSTAGE-DESIGNER

    Important features of the MOSFET to focus on are the max ratings of the Drain-source voltage, drain current and also the gate charge. The VCC regulation voltage of LM5177 is 5V and it needs to be able to drive the MOSFET.

    For the clock, you can use the clock generator suggested in the app note if the clock team doesn't have a better suggestion.

    Best regards

    Yezi

  • 0 in reply to Yezi Yang
    TI__Mastermind 22300 points

    Yezi,

    I am not certain if the LMK01801 (driven by LMK6C) can support digital delay for this low of a frequency range (<= 600kHz) - I have assigned this to our buffer expert for further investigation.

    Thanks,
    Kadeem

  • 0 in reply to Kadeem Samuel
    TI__Mastermind 29002 points

    Hi Yezi, 

    This is possible with this device. 
    One suggestion I have - make the output frequency the ref clk divided by 8 - this guarantees you can meet the 90,180,270 deg phase shift with the following settings. 

    So, in other words, if you have output set to 500kHz make the ref clk 4.5MHz - this will make the ratios the same as table 9-3 and now you can just set CLKOUT12_13_DDLY to 7 and CLKOUT12_13_HS to zero which results in a relative digital delay of 2.0 steps which is a 90-degree phase shift. 

    If you don't choose to follow this - you will find yourself forced to manually do the math to calculate the respective half period and relative digital delay steps to create the phase shift you require. 

    Best regards, 

    Vicente