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information about lm2576.

i want to design dual power supply with  high current rating ,i am not familiar with lm2576.

can anybody tell me how to use lm2576 negative (-5 volt) generation. please reply me i am waiting .



  • In reply to Luke Pan:

    Also I saw LM7905 is a negative output LDO for max 1.5A output. So for the -5V/5A negative output, I'm afraid you need an negative output controller.



  • Hello Yogesh,

    Perhaps I can provide some help here.  First, if you are using a center-tapped transformer secondary then you need to tie the center tap of the transformer to the center of two output capacitors. This provides separate positive and negative dc sources for the two regulators in your application. Without this connection there isn't a midpoint ground reference for either regulator to act upon and it will not function predictably, if at all. Once that correction has been made there is a second issue that often causes issues with heavy loads connected across symmetrical supply regulators.; that of a startup issue where one or the other supply regulator fails to start up. This can be resolved by placing reverse biased Schottky diodes across each of the two supply outputs. I have illustrated both suggestions in the attached schematic. Thank you. Lets us know your progress. AlanYogesh.pdf

    Alan Martin  - Wide Vin Applications Wrangler (retired)

  • In reply to Alan Martin:

    thanks for your response,

    i will try this on my circuit and let you know the result.and i have one doubt , i used  1000uf cap as a filter capacitor is there any effect of this. should i switch to 2200uf .

    thanks yogesh

  • In reply to yogesh nandurkar:

    The following schematic might not have attached to my earlier response. (Can't tell from my browser.)


    Alan Martin  - Wide Vin Applications Wrangler (retired)

  • In reply to yogesh nandurkar:

    This schematic using an AC input via a bridge rectifier will need a center tapped transformer to generate the independent raw +and - voltages into each rail regulator.

    A better approach is to use two buck regulators, one in conventional buck configuration to create +5VDC. The second one in inverting buck-boost for the -5V rail as shown in Ap Note SNVA722B by Anston Lobo.

    Each of these regulators will need a reverse biased Schottky diode placed across it's output to insure correct start-up since the end application can pull current from one rail to the opposite without conduction through the common ground.

    Alan Martin  - Wide Vin Applications Wrangler (retired)

  • In reply to yogesh nandurkar:

    Consider the following approach. Refer to SNVA722B


    Alan Martin  - Wide Vin Applications Wrangler (retired)