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Thread: Is possible to get 12v/10amp, 3.3v/10amp, 5v/10amp from LM2678 chips?

  1. #1
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    Is possible to get 12v/10amp, 3.3v/10amp, 5v/10amp from LM2678 chips?

    Hi all !!

    First of all in not a Electronics Expert but one person with basic knowledge of analog electronics.

    I have found the LM2678 chip interest for dc-dc PSU and i have some questions to Sproggy and Mastero gurus.

    Is possible to get 12v/10amp from 2 x LM2678-12 chips in parallel instead of 1 x LM1084IT-12 chip and 1 x LM2587T-ADJ chip (MASTERO 4.5 design)
    and 3.3v/10amp from 2 x LM2678-3.3 chips in parallel instead of 2 x MAX788 chips (MASTERO 4.5 design)
    and 5v/10amp from 2 x LM2678-5 chips in parallel instead of 2 x MAX787 chips (MASTERO 4.5 design)

    Is something wrong with the Typical Application Diagram from LM2678 ?

    Have someone tried this design ?

    Thanks.


  2. #2
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    How exactly were you planning on putting them in parallel?
    I have found you an argument; I am not obliged to find you an understanding.

  3. #3
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    This is my question to forum :
    How exactly can i putting LM2678 chips in parallel to get the desired amps and volts ?

    i have founded one solution (look at attachments).
    But i expect some help out there !!

    Thanks
    and sorry for my english
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  4. #4
    lez
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    Is the comp pin input or output, surely it cant be both.

    I would build 2 seperate circuits and join the outputs with a diode and 0.1ohm resistor, after all both coils wont produce the same output voltage for the same PWM due to differences in the windings.

    Lots of commercial designs do it that way, good or bad it works.

  5. #5
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    Hi lez,

    I think that this schematic is 2 seperate circuits and the outputs are joined together to share the load current demand.
    I provide the above schematic with 1 LM2577 chip

    Lez can you send me one better design ?

    Can anyone tell me why mastero use 2 x MAX788 chips to produce 3.3v and not 2 x LM2678-3.3 chips in parallel and 2 x MAX787 chips to produce 5v and not 2 x LM2678-5 chips in parallel?

    Thanks
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  6. #6
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    Its easy to get Samples from Maxim.

  7. #7
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    Take a look at Sproggy/Mastero Mk4.0 thread . The thread has 4.0 and 4.1 design in there. 4.0 use National Semi LM2678 chips for 3.3V and 5.0V. The design doesn't work so well so the 4.1 come out to replace the LM2678 with the MAX chips.
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