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LM5157: Custom Circuit Design Check for LM5157

Gencay Akyuz
Intellectual 265 points
Part Number: LM5157

Greetings, 

I designed the LM5157 circuit according to its eval board. Input voltage is regulated 5V and output is 12V 1 - 1.2 A. 

I made some changes on some of the components. Red text near that component is eval board values, so 

  •  Are new resistor values okay for UVLO?
  • I won't use PGOOD can i leave this pin floating?
  • In eval board C65’s voltage rating is 100V. Can I use a 50V voltage rating 0402 capacitor?
  • In eval board C64’s voltage rating is 16V. Can I use a 10V voltage rating capacitor?
  • For the L20 inductor can I use 2.2uH instead of 1.5uH (part number of inductor : SRP1265A-2R2M)
  • I selected new resistors for FB. Are FB resistors suitable? 

  • 0
    TI__Mastermind 47141 points

    Hello Gencay,

    thank you for using the E2E forum.

    For getting the external values you can also use the Quickstart calculator which can be found on the product page:

    LM5157 data sheet, product information and support | TI.com

    If PGOOD is not used, you should connect it to GND or use a pull up to VCC.

    For RUVLO,lo = R52 this would give then 100k (see Quickstart calculator)

    Both lower Capacitor Ratings should be OK

    FB resistor is OK.

    Using a 2.2uH inductor should be OK but check with the Quickstart calculator if you get all the parameters you need for your application.

    Best regards,

     Stefan