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LM25141: Potential Webench Power Designer bug when selecting another switching frequency?!

Matthias Wendt
Prodigy 10 points
Part Number: LM25141
Other Parts Discussed in Thread: LM5141

Hello!

I try to re-simulate an existing design using the LM25141RGER or LM25141QRGERQ1 to generate 5.20V @ 7A from 18V-38V with ~ 340kHz switching frequency.

If I select a switching frequency of 2.2MHz the Rt shows up in the schematic and I can customize the switching frequency. If I select a # of 440Hz the Rt doesn´t show up in the schematic and I cannot customize the switching frequency. When changing the switching frequency manually it always switches back to 440kHz as soon as I press “redesign”.

I have the pdf of the Webench simulation a colleague generated in 2018. During that time it was possible to use different switching frequencies (e.g. Rt = 73.2kOhm resulting in ~ 302kHz). So it worked in the past.

So how can I start today a simulation with 340kHz instead of 440kHz?

Best regards,

Matthias

  • 0
    TI__Guru 56702 points

    Hi Matthias, 

    I will refer this to our WEBENCH team. In the meantime, I recommend using the LM5141 quickstart calculator to design your circuit.

    Regards,

    Tim

  • 0
    TI__Expert 8365 points

    Hi Matthias,

    The RT pin doesn't appear in the schematic for 2.2MHz and 440KHz frequency as these frequency selection is done by OSC pin as given in datasheet below. 

    RT appear in the schematic only if user enters the preferred frequency in the advance user option shown below.

    We have fixed this issue. The changes will be available on ti.com in next release cycle by end of first week of November. We will let you know once it is available.

    Thanks & Regards,
    Praveen