• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 507 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM258x-ADJ component scaling

Bob Day1
Prodigy 80 points
Other Parts Discussed in Thread: LM2588, LM2585

Hi,

We're looking to use a 258x-ADJ part for a triple output supply, using one of the specified Coilcraft/Pulse etc transformers.  Question is, the outputs are spec'd at +/- 12V and 5V, and we need to run at about 40% higher voltages - +/-17V, 7V (to get to +/-15 & 5V after LDO regulators).  Other than increased current & dissipation issues, is there a reason we can't use the same transformer as spec'd in the 2586 or 2588 datasheet, using an -ADJ part?  Thanks.

  • 0
    TI__Mastermind 23815 points

    Hi,

    What particular transformer that you want to use? Is the input voltages and output currents are the same as the table 1 on page 15 of the datasheet?

    You need to check whether the transformer saturate when your current is higher than what is written on the datasheet. 

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Prodigy 80 points

    Q4344 from Coilcraft 1:0.8:0.8:0.35, ~80uH Primary.  The secondary currents we are using are lower - 1/2 actually - and we'd like to run it at close to 200kHz with a 2558 part.  Assuming as you said the limiting factor is the primary current... - we'd be going up 40% in secondary voltage at 1/2 the design current.

    By the way, are these parts any different other than the feedback voltage?

    Thanks

    -Bob

  • 0 in reply to Bob Day1
    TI__Mastermind 23815 points

    Sorry for the late reply Bob, but yes please double check the current in the primary and not exceeding i think about 3A so you don't lose the inductance.  Also double check your volt-usec and not exceeding the value in the datasheet of the transformer.

    As for LM2585 and LM2588, for either parts you can have an adjustable version. They are similar in terms of control but have a noticable difference also. A couple of differences are LM2588 have 5A current capability compared to 3A on the LM2585. Also, you can adjust the switching frequency on the LM2588 whereas the LM2585 has a fixed switching frequency of 100kHz.

    Thanks, hope that helps

    -Arief 

  • 0
    Genius 3945 points
    I am considering doing exactly this -- how did your design work out?