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Rrequired output is 5V,150mA

stain b
Prodigy 40 points
Other Parts Discussed in Thread: LM2674, LMZ14201, LM317, TL317, LM3103, LM22675, LM2841, TPS54140

HI,

      In my circuit , required output is 5V,150mA.My input voltage is 10v-42v. I plan to use LM317KC(TO-220) & UA7805(TO-220) .

      Can you please comment about this one or otherwise tell me some other suggestions.

Thanks ,

B.stalin.

  • 0
    Expert 1920 points

    I wouldn't use the linear regulators. At 42V input you would dissipate 5,55W total in just your regulators to get 0,75W out ! (efficiency < 12%!).

    If your input could get below 40V then I recommend the LM2674. It runs from 8-40V.

    http://www.ti.com/lit/ds/symlink/lm2674.pdf 

    On page 1 the circuit is shown.

    I can't remember any cheap ICs which can 42V, but they're there :-)
    I know the LMZ14201 can, but it's 1A out and costs around 11 USD on Farnell. 

  • 0 in reply to CWilson
    Prodigy 40 points

    Thanks for a reply.

     But my problem is i am very comfortable with linear regulator's(i don't have any experience with inductor). Actually  my input voltage is varied from 10v to 42v.If

    i use this two regulators LM317KC(TO-220) & UA7805(TO-220)(even efficiency is low ) can i get the uninterrupted output(5v,150mA) or it will affect  LM317KC

    in anyway.My plan cost  also less than 1USD.

  • 0 in reply to stain b
    TI__Guru*** 142926 points

    Stain

    It can be done. set the LM317 to regulate the input to 24V output (exact value not important) then use uA7805 to regulate that down to 5V.

    When the input is 42V the LM317 dissapates (42V-24V)*0.15A = 2.7W and uA7805 dissipates (24V-5V)*0.15A = 2.85W
    When the input is 10V the LM317 dissipates (10V-2V)*0.15A = 1.2W and uA7805 dissipates (8V-5V)*0.15A = 0.45W (TL317 full on)

    You could just use the LM317 alone if you dropped the max input to 40V by adding three or more diodes to the input pin.
    In all case a heat sink(s) will be required.

    Regards,
    Ron Michallick

     

  • 0 in reply to CWilson
    TI__Genius 10095 points

    There are  many fairly simple to design switchering regulators that can operate from 42Vin and have 5V 150mA output voltage.

     

    If you go to the TI home page. WWW.TI.COM you will see on the bottom right a tool called Webench.  Enter your design criteria.  You will receive the following list.  All of which come with a BOM, and most of which will have recommended layouts in their documentation.

    Results Include

    LM3103

    LM22675

    LM2841

    TPS54140

    Regards,

    Marc