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LM22677-5.0V Output Regulation Problem

Jan Stoop
Prodigy 10 points

Good day,


I am new at designing power supplies and I am designing a power supply with the following specs:

  • Vin = 9 – 36Vdc
  • Vout = 5Vdc.
  • Imax = 5A.


I am experiencing an unusual regulation issue in the LM22677-5.0V and am seeking ideas or if anyone else has experienced a similar effect or has any explanations.


When I power the regulator it does not regulate to 5V but keeps on increasing with the input voltage. The output always seems to be 3V below the input voltage (ex. Vin=10V, Vout=7V ).
I have tried numerous circuit mods with no major changes in this behaviour.

  • 0
    TI__Genius 10115 points

    It sounds like you might have a bad solder connection on FB.  If FB is open the device will go to max duty cycle and will follow VIN.

    Try looking at this connection first.

     

    Regards,

    Marc

  • 0
    TI__Guru 72685 points

    The most important aspect of any switching regulator is the PCB layout.

    You can find the following app notes on the TI website, that may help:

    SNVA021C, SNVA054C, SLUO230

    Also, did you use Webench to design the regulator?  That can be very helpfull to get the design to work the first time.

    If you send me your shipping address and phone to the following email, I will send you an EVM that you can use to help you get a working design:  SimpleSwitcherApps@ti.com

    FD