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LM25183: LM25183 transformer

Shinu.V.Mathew
Genius 10390 points
Part Number: LM25183
Other Parts Discussed in Thread: LM25180, LM5180

Hi Team,

My customer selected LM25183 for 5W DC-DC to dc converter for a gate driver power supply application, specification as given below. 

Isolated DC-DC flyback converter

Vin : 22 - 26 V DC

Vout : 20VDC

Io : 250mA

Po : 5W

 The webench design shows peak current for this design is 1A for 9.3uH primary inductance and 350kHz switching frequency. But on calculations getting around 3.25A peak for the same. Can customer directly go with webench design and use specified transformer (749196331).

Please help with your inputs. 

Regards, Shinu Mathew. 

  • 0
    TI__Guru 73652 points

    Hi Shinu,

    I recommend using the LM25183/4 quickstart calculator to get an idea of transformer design (min. mag inductance, turns ratio, etc.). The sat current must be higher than the peak current limit (2.5A for the LM25183).

    Based on your specs of 20V/0.25A (5W) and 22-26Vin, there should be no need to use the LM25183 - the LM25180 can meet this power requirement with a smaller-sized transformer. Please check with the LM25180 quickstart calculator. A 1 : 1.5 or 1 : 2 transformer turns ratio seems feasible (target a max duty cycle of 40-60% depending on how low Vin-min is). For evaluation puposes, take a look at the LM5180 dual-output EVM (+15V, -7.5V is close to your 20V output requirement). The datasheet provides a part number for a suitable Coilcraft single-output transformer (see Coilcraft's website for more detail). 

    Btw, the quickstart calculators are available by download from the respective product folders. 

    Regards,

    Tim