• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 211 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.

LM51231-Q1: How to choose the low and high MOSFET.

sun qiyun
Intellectual 280 points
Part Number: LM51231-Q1

Tool/software:

Hello,

I am Sunny.

I want to use LM51231-Q1 to design a 24V ~48V 300W boost circuit.

The low and high MOSFET selection is very important for me as the power is very high and the two MOSFETs may are very hot.

Could you please help recommend the MOSFETs alternates that has good heat release performance in this design? 

I choose 434khz as its switching frequency, but it seems too high for this 300W application. Please help recommend together.

Thanks in advance.

  • 0
    TI__Mastermind 19625 points

    Hello Sunny,

    The gate drivers of the LM5123 are made for Dual FET usage (two low side FETs and two high side FETs).
    This helps to distribute the thermal dissipation across the PCB.
    See our EVM: https://www.ti.com/lit/ug/snvu737a/snvu737a.pdf

    In the BOM you can see that we are using NTMFS5C670NLT1G FETs on that EVM.
    Our customers are also using FETs from the buk9y series.
    These FETs are using a 5x6 mm package.
    For this power level, please do not use any FETs in a 3x3mm package nor dual FETs in one common package.

    Please understand that I cannot comment on the thermal characteristics of the FETs.

    The other component that is dissipating quite some heat is the inductor.
    Please leave a lot of margin on top of the saturation current and select an inductor with a high efficiency / a very low DCR to minimize losses.

    For a proper calculation of the required external components, please use the QuickStart calculator which you can download here:
    https://www.ti.com/tool/LM5123-Q1-DESIGNCALC

    This calculator also supports a calculation of the Losses of the FETs and the overall efficiency.
    It confirms that there are less switching losses when the switching frequency is decreased.

    Best regards
    Harry

  • 0 in reply to Harry Hofner
    Intellectual 280 points

    Hi, Harry

    Thanks for your reply.

    I will calculate the MOSFET parameters based on the reference.