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LM3488 MAX VOUT

WhiteHorse
Genius 4430 points
Other Parts Discussed in Thread: LM3488, LM3481

E2e,

What is the max Vout for the LM3488?

Regards,

WH

  • 0
    TI__Guru 71516 points

    Hi John,

     For Vout, I'm guessing you are referring to the voltage at the DR pin, correct?  If so, the ABSMAX is shown on page 3 is 8V.  Of course we do not want to operate at MAX, so the recommended operating specification is shown on page 5 as a function of VIN.  For VIN up to 7.2V, then VDRmax = VIN; for VIN > 7.2V, VDRmax = 7.2V.  Also see footnote (1) at the bottom of that table.  Recognizing that 7.2V is shown as TYP for VIN > 7.2V, the 8V stated as VDRmax on page 3 would be the absolute maximum seen on that pin.  Note also that the TYP values are spec'd with a VIN = 12V.

    Also see Fig 6 on page 7.

    ~Leonard 

      

  • 0 in reply to LeonardEllis
    Genius 4430 points

    Hi Leonard,

    Actually wanted to know the highest output voltage it could produce.  I have been able to simulate on WeBench an output of 40V @ 200mA and120V @ 10mA.  I know that max power will limit the output voltage it can generate as well as DR.  What would be the max output voltage the LM3488 could generate to drive a load?

    Thanks for your help. 

  • 0 in reply to WhiteHorse
    TI__Guru 71516 points

    WH,

    Seems there might be an error in the model as it should follow the datasheet specifications, VDR = 8V ABSMAX.  Please send the SIM file and I'll see if the Webench experts can figure out what is happening.  Also, what is VIN in your model, as VINMAX is 40V, ABSMAX of 45V, so to get 120V VDR, wow!

    ~Leonard 

  • 0 in reply to LeonardEllis
    Genius 4430 points

    Hi Leonard,

    The file is attached.

    LM3488 9.6V in 40Vout @200mA.pdf

    Regards,

    WH

  • 0 in reply to WhiteHorse
    TI__Guru 71516 points

    VOUT is not at the DR pin, and this is the 7.2V I was referencing. The design you provided is configured in a BOOST topology, so the final VOUT can indeed be greater than the VIN and control signals of the LM3488. 

  • 0 in reply to LeonardEllis
    Genius 4430 points
    Thanks Leonard. What would the highest Vout the LM3488 could achieve in a boost configuration?
  • 0 in reply to WhiteHorse
    TI__Guru 71516 points

    I was hoping we had a graph that conveyed this, but alas, we do not.  This will, of course, depend on all the circuit requirements, and you can get close by using Webench and varying the parameters.  For example, we set VIN = 40V, VOUT = 235V at 10mA load, and this was successful.  Mostly it is going to depend on the external components, i.e. the FETs used.  If you have some specific requirements, we may be able to create a more defined designs.


  • 0 in reply to LeonardEllis
    Genius 4430 points
    Thanks Leonard!
  • 0 in reply to WhiteHorse
    TI__Expert 6860 points
    Hi,
    May I know what is your application requirement .

    You can use flyback topology on LM3481 and get very high ratio step up as well as step down . You can reference below TI design for high ratio step up .
    www.ti.com/.../PMP10666

    People also use Boost in high ratio step up configuration (say from 5V to 250V) where they employ boost first followed by voltage doubler or quadrupler if the output power requirement is less .

    Ambreesh Tripathi