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LP2986: External resistor for adjustable output voltage

Alan Chang
Intellectual 1960 points
Part Number: LP2986

Hi,

   A question about LP2986 external resistor for adjustable output voltage,  on data sheet, 8.2.2.1

  "The resistor connected  between the FEEDBACK pin and ground pin should be 51.1 Kohm."  

  Can I change it to the other value, saying 100 kohm for power saving? if not, why? if not, 51.1 kohm is fixed already, right?

  • 0
    TI__Expert 3995 points
    Hi Alan,

    The 51.1 kOhms is to to ensure a 25uA of current flowing through the divider which in turn ensures accuracy since the device was customized using this resistor value. The current sinking into FB pin is 150nA which is ~170 tiny compared to 25uA sinking through the divider with the 51.1 kOhms resistor, so by making the resistor small (100 KOhms ) this ratio will be half from the customization ratio thus accuracy will derailed and that's why the datasheet emphasizes the resistor should be 51.1 kOhms. Hope this explanation helps!

    BR,
    Haidar