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TPS563240: Followed Webench Power Designer Schematic - have unexpected results

James VDC
Prodigy 240 points
Part Number: TPS563240
Other Parts Discussed in Thread: TPS563212, LP3872

I used the Webench to design a buck converter using TPS563240.  I utilized the TPS563249EVM PCB to prototype the design, changing all parts as necessary (including TPS56240).

The design characteristics were: 5.5-9VDC input / 5.1VDC / 2A output - with the actual output current range to be .015 - 1.5A.

The various input voltage and output current scenarios check out without any errors within Power Designer and in fact the data results even look very promising across that range.

However, in application, the output doesn't reach 5.1VDC until the input is between 8-9VDC, depending on output current draw.

Does the Webench Power Designer not account for the dropout calculations in the datasheet for the TPS563240?  It seems that it would have to in order to be a fully useful tool?

Thank you

  • 0
    TI__Expert 8100 points

    Hi James,

    Based on the minimum off time in datasheet, maximum duty cycle under 1.4MHz is 65%. If Vout is to be held at 5.1V, the minimum Vin should be around 8V by calculation. 

    Webench also gives alert when conducting simulation, showing that the minimum Vin is supposed to be greater than 7.9969V for Vout to be regulated.

    BRs

    Zixu

  • 0 in reply to Zixu Wang
    Prodigy 240 points

    Hello Zixu,

    Interesting, no such "Dropout Condition" warning appeared for me.  Is this a popup window?  Or, where can I find the "Alert Center" for future situations?

    James

  • 0 in reply to James VDC
    TI__Expert 8100 points

    Hi James,

    The notification will appear upon entering webench power design website after clicking "open design" button.

    If you want to find the notification of "Alert Center", you can click the "doorbell" button besides the "EXPORT" button.

    BRs

    Zixu

  • 0 in reply to Zixu Wang
    Prodigy 240 points

    Thank you so much Zixu, that was very helpful.  I was unaware that the bell icon was present / an indicator of an alert.  This will be useful moving forward with other designs.  Would you happen to have a recommendation for an alternate IC that has a static/fixed frequency of 1MHz or greater across my entire desired current range of approximately .01 - 1.5A?

  • 0 in reply to James VDC
    TI__Expert 7430 points

    Hi James

    TPS563212 would be a good choice for you. BTW, would you please tell me the end equipment of your application? And if possible would you please tell me the TAM of the project?

    Thanks.

    BR

    Ruby

  • 0 in reply to Ruby Li
    Prodigy 240 points

    Thank you Ruby.

    I am working on a 5V supply to power a product / charge its internal battery.  The intended market is for that specific product only and therefore very niche.  At present I am simply prototyping options.  I considered using LP3872 but found the transformer regulation would not be sufficient.  I also do not want the waste associated with a traditional Linear regulator IC.  With your suggestion I am trying ot decided between the TPS563240 and now the TPS56212.  I am finding pros and cons to both.

  • 0 in reply to James VDC
    TI__Expert 7430 points

    Hi James

    Good to know. If there is any support needed from my side, feel free to contact. I am going to close this post.

    Thanks.

    BR

    Ruby