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LM2577: LM2577S-ADJ/NOPB

Santhush Loku
Prodigy 10 points
Part Number: LM2577

Hi All,

I am using the LM2577S-ADJ/NOPB converter to step up the voltage to 12v. 

However it is only outputing 8.3V and also making a buzzing sound. 

Any ideas, what could be wrong?

  • 0
    TI__Genius 16515 points

    Hello Santhush,
    Thanks for reaching out to us via e2e.

    Connecting the feedback pin to VOUT as shown in figure 37 in the datasheet will only work for devices with a fixed output voltage like the LM2577-12.
    When you are using the LM2577-ADJ, you have to use an external feedback divider (as shown on page 2) and calculate the resistor values as described under Point 3 on page 20.
    In general, please select all external components according to the STEP-UP REGULATOR DESIGN PROCEDURE from page 16 onwards.

    So, please either replace the LM2577-ADJ with an LM2577-12 or implement the feedback divider.

    Best regards,
    Harry