• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 518 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.

changing output voltage on LM5576 Evaluation Board

hallo knallo
Prodigy 20 points
Other Parts Discussed in Thread: LM5576EVAL, LM25576, LM5576

hi

is it possible to change the out put voltage of the lm5576eval board, or to even make it flexible with cahning an resistor for an potentiometer?  I need output volage between 5 and 14 Volts?


and another question: is there any difference between the lm25576eval board and the lm5576eval board.

could i just change the lm25576 against the lm5576 to get a higher range of input voltage up to 75 volts???

thanks in advance

gernot

  • 0
    TI__Genius 15810 points

    Hello,

    The LM5576 will regulate a voltage set by the resistor divider at the FB pin. The entire BOM on the board is calculated based on the duty ratio of Vout to Vin. If Vout is changing, you would need to change the BOM too. Therefore, ideally, if you want the best performance, then you would not dynamically change Vout on the LM5576 design. 

    Although if you must, you could design the BOM for the worst case condition from your set of Vout. In your case it would be your minimum Vout. Then you should be able to regulate to other Vouts, but the performance might not be at its best.

    The difference between the two boards could be the rating on the input capacitors. If you decide to use the same board for the LM5576, make sure that the input caps have the right voltage rating on them.

    Regards,
    Akshay

  • 0 in reply to Akshay Mehta
    Prodigy 20 points

    thanks,


    performance is not what i need i just drive a high power leds with it.


    Any idea or tip what rated resistor will change the vout to 12 Volt or what potentiometer is goot to replace instead of the resistor?

    thanks

    gernot

  • 0 in reply to hallo knallo
    TI__Genius 15810 points

    Hello,

    You could use the following information to size the resistors.

    Rfbtop/Rfbbot = (VOUT / 1.225V) - 1 

    For a 5V output, the Rfbtop/Rfbbot ratio calculates to 3.082. The resistors should be chosen from standard value
    resistors, a good starting point is selection in the range of 1.0kΩ - 10kΩ. Values of 5.11kΩ for R5, and 1.65kΩ for
    Rfbbot were selected.

    If you want dynamically change-able output, then you could substitute the lower feedback resistor with a pot that has the range to give you the two extremes of voltages.

    Regards,
    Akshay