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WEBENCH® Tools/LM5180DESIGN-CALC: LM5180

Part Number: LM5180DESIGN-CALC
Other Parts Discussed in Thread: LM5180

Tool/software: WEBENCH® Design Tools

This is regarding LM5180 power supply.

Input voltage : 12-15V

Output Voltage : 15V

Output current : 0.2A.

1) I have calculated the resistor, capacitor values based on the formulaes provided in LM5180 data sheet. With this values i tried to simulate the circuit but expected output is not coming (used RM core transformer). operated in FFM mode.

 2) In WEBENCH power designer we got some schematic with the same input and output voltages. But as per the requirements the resistor values (feedback) and some other resistor values are not matching with the calculations as per the data sheet formuales. Please look and resolve this issue.

Attached files for reference. Anticipating early reply.

LM5180-Q1_1_6-27-19 (1) 30 march_ with my tf - autosave 20-03-31 15_52.TSCexample lm5180 - autosave 20-04-03 12_33.TSC

  • In the second file titled "example_lm5180.." there needs to be a Diode from SW to VIN to loop back that transformer current.

    The Zener may not always be necessary but the DF diode is.

    Also the EN resistor arrangement is incorrect. Did WEBENCH give you this?

    The FB resistor and turns ratio sets the output voltage. Both the FB resistors are similar (154kΩ and 157kΩ) for a 1:1 transformer. 

    It is related to the standard value selection.

    Please post your completed LM5180DESIGN-CALC file.

    -Orlando