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LM5116: About the sync buck converter design

Onur Keskin
Intellectual 390 points
Part Number: LM5116
Other Parts Discussed in Thread: PMP7282, LM555, LM5143-Q1, LM5143

Hi,

I will design a buck converter with two LM5116.I need a high current. Therefore, i will use sync design .

The design I found is 2 phase buck converter(PMP7282 Two-phase buck converter ). I intend to take this design as a reference.

*My input voltage will be single phase dc. What should I pay attention to in sync design for single phase?

*In the dual design I have found, there is a separate EN and UVLO input for both ICs.  Are there any pins that can be used in sync design? For example, can EN and UVLO inputs be used together sync design? 

*Error comparator designed externally. Should I change?

*The synchronization clock is generated from LM555. However, the phase difference between the two IC's was created (180 degrees). Is this phase difference a design specific to a 2-phase inverter?

  • 0
    TI__Guru 73752 points

    Hi Onur,

    If Vin-max is less than 65V, please consider the LM5143-Q1 two-phase controller. It’s a higher performance and easier solution to implement than two LM5116 controllers.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Intellectual 390 points

    Hi Tim.

    The input voltage must support 80 volts. What exactly is the two phases ? Is the phase difference only for performance purposes?

  • 0 in reply to Onur Keskin
    TI__Guru 73752 points

    Hi Onur,

    The LM5143-Q1 datasheet has more information on using two phases as a buck regulator solution. Basically, each of the two phases carries half the load current, resulting in thermal spreading and smaller power stage components. Also, because the two phases operate 180 degrees apart, there is ripple current cancellation in the input and output capacitors, leading to lower voltage ripple.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Intellectual 390 points

    Hi Tim,

    Thanks for information. ,

    I must use lm5116 because my input voltage will be high. I'm taking reference to PMP7282. On the PMP7282 both ICs are designed discrete. I need to control the UVLO and the EN pins together. At least I should be able to use these pins together.This is what I want to learn.

    No problem with lm5143 applications. I understand but as I said I can't use it.

    What are your recommendations for lm5116?

  • 0 in reply to Onur Keskin
    TI__Guru 73752 points

    Hi Onur,

    You can follow the schematic connections of the PMP7282 two-phase design and update the FET choice as needed for the 80V max Vin (i.e. use 100V FETs). Depending on the output current requirement, one high-side and one low-side FET per phase may be sufficient. It may be beneficial to connect the EN pins together so that both ICs are enabled simultaneously. Also, tying the UVLO pins together with one UVLO divider ensures that both phases start at the same input voltage threshold. 

    Regards,

    Tim