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WEBBENCH Designer having issues designing with LM5116MHX/NOPB switching controller

Mohan Unnithan
Prodigy 10 points
Other Parts Discussed in Thread: LM5116

Hello,

I am trying to use WEBENCH designer to design a 5V, 7A power supply using TI's switching controller LM5116MHX/NOPB similar to an example in TI datasheet for LM5116.

However, I am getting the following message from the WEBENCH designer: "CAN'T FIND SUITABLE FET FOR THE DESIGN. TRY REDUCING THE CURRENT".  I cannot reduce the current as my design requires 7Amps.

Is there anyway to override this error? TI datasheet for LM5116MHX/NOPB has a design for 5V/7A with a switching freq of 250KHz just like what I am trying to do.  How was that design done if the WEBENCH tool cannot find a suitable FET?

The following are the input/output details of the design:

VIN Range = 10V - 60V

VOUT = 5V,  IOUT = 7A

Switching Freq: 250KHz

TAmbient = 50C

TI SWITCHING CONTROLLER: LM5116MHX/NOPB

MOSFETs: VISHAY SIR870ADP-T1-GE3

Thank you for your help.

Regards,

Mohan Unnithan

Allied Telesis

  • 0
    TI__Expert 6365 points

    Hi Mohan,

    Please try to create your design with the ambient temperature set at 10 degree C. This should allow you to create a design. Please note that the max frequency of the design may not reach 250kHz. This means that you may have to reduce the ambient temperature a bit more (~5 deg. C). Once the design is created, You can adjust the design ambient temp back up to 50 deg. C to run thermal simulation. The thermal sim will show the components dissipating the most power. The expectation is all component temperatures should be less than 150 deg. C. Please keep in mind that WEBENCH uses only Theta JA values for its initial calculation of the BOM. As you know, attaining the BOM is only beginning of the design. The board design in all cases is more critical.

    Please let us know if you have more questions with WEBENCH.