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WEBENCH® Tools/LM5157-Q1: availability of the IC and result in Webench

Xavier Queffelec
Intellectual 310 points
Part Number: LM5157-Q1
Other Parts Discussed in Thread: LM5157, TPS55340,

Tool/software: WEBENCH® Design Tools

Dear support Team,

I am looking for a DC/DC step-up converter and Webench proposed to me the LM5157 & LM51571 chips.

Design: supply input 20 V to 25V / supply out 34V / current max 3A / 40°C temperature integrated transistor

I made the simulation with Webench and I get a capacitor for Cout "custom" Cap= 3.01868 uF / ESR= 1.0 uOhm / VDC= 51.0 V / IRMS= 3.7022 A

This is quite strange as usually Webench use "real" devices for it's simulation, so it why I am contacting you.

After this simulation I check the datasheet of the chip and I saw that this one is realy new and only preview stage.

Can you tell me when this chip will be release as I am planing a small redesign of an existing board?

Concerning the Webench simulation, can you told me if there wrong in Webench concerning this chip?

Many thanks for your help.

Best Regards,

Xavier

  • 0
    TI__Mastermind 21720 points

    Hi Xavier,

    Thanks for reaching out with your question and for considering the LM5157 in your design.

    You are correct the LM5157 is in preview mode and it will probably be a few months before the product is fully released. If you are looking for a device that is fully release the TPS55340 would be a good fit for this application.

    The WEBENCH is just suggesting that a capacitor with a 50V rating and close to 3uF of capacitance. I would suggest using a 4.7uF capacitor that is rated for 50V.

    Please let me know if you have any questions.

    Thanks,

    Garrett 

  • 0 in reply to Garrett Roecker
    Intellectual 310 points

    Dear Garrett,

    Many Thanks for your answer. Sorry for my late reply - I didn't get any mail that you already send me an answer to my question.

     I already consider the TPS55340 for the design but I had some Problem with the Simulation in Webench:

    With 20V Input this solution was not available for 3A - I was limited around 2.5A for the design. Only with 24V Input I was able to reach 3A.

    There is also an other issue the total "Power Power Dissipation" raised up 50% from ~2.2W to 3.25W which is not so nice.

    This afternoon we will discuss the solution - the Step-Up DC/DC is only one of 3 possible solution to improve the actual design.

    So if we decide to made this Step-Up solution and I still consider using the LM5157, will it be possible to buy some sample of this chip?

    Many Thanks for your help.

    Best Regards,

    Xavier

  • 0 in reply to Xavier Queffelec
    TI__Guru 58215 points

    Hello Xavier,

    If you go to the LM5157-Q1 product folder down to ordering: 

    You can find the XLM5157QRTERQ1. This is the pre-production material you can already order. As the part is not released, only the X marked devices are available. The X at the beginning indicates that the device is not in full production yet and the behavior of the final material might be somewhat different.