Figure 2-2 shows the FB network circuit.

Converter DC regulation forces V_FB = V_REF = 0.6 V. Therefore, the divider is injecting current i_INJ into the FB node to offset the output voltage.

1. Calculate VOUT as a function of i_INJ

   KCL at FB node:

   Equation 1.
   

   

   
   

   Rearrange and simplify as Equation 2 shows:

   Equation 2.
   

   

   
   
2. Solve for i_INJ
   Equation 3.
   

   

   
   

   KCL @ X to solve for Vx:

   Equation 4.
   

   

   
   

   Rearrange and simplify as Equation 5 shows:

   Equation 5.
   

   

   
   
3. Substitute:
   Equation 6.
   

   

   
   

   where V_x equals Equation 5.

These calculations are integrated in the TPS40322 Resistor Divider Vout Offset Calculator tool.