With the small signal models coming out, the next step is to calculate the compensation network parameters with the given inductor and output capacitance.

1. Set the Cross Over Frequency, ƒ_C.

   The first step is to set the loop crossover frequency, ƒ_C. The higher crossover frequency, the faster the loop response is. It is generally accepted that the loop gain cross over no higher than the lower of either 1/10 of the switching frequency, ƒ_SW, or 1/5 of the RHPZ frequency, ƒ_RHPZ. Then calculate the loop compensation network values of R_C, C_C, and C_P by the following equations.

2. Set the Compensation Resistor, R_C.

   By placing ƒ_Z below ƒ_C, for frequencies above ƒ_C, R_C | | R_EA ~ = R_C and so R_C × G_EA sets the compensation gain. Setting the compensation gain, K_COMP-dB, at ƒ_Z, results in the total loop gain, T_(s) = K_PS(s) × H_EA(s) being zero at ƒ_C.

   Therefore, to approximate a single-pole roll-off up to f_P2, rearrange Equation 17 to solve for RC so that the compensation gain, K_EA, at f_C is the negative of the gain, K_PS, read at frequency f_C for the power stage bode plot or more simply:

   Equation 21.

   where

   • K_EA is gain of the error amplifier network
   • K_PS is the gain of the power stage
   • G_EA is the transconductance of the amplifier, the typical value of G_EA = 70 µA / V
3. Set the Compensation Zero capacitor, C_C.

   Place the compensation zero at the power stage R_OUT ,C_OUT pole’s position to get:

   Equation 22.

   Set ƒ_Z = ƒ_P, and get

   Equation 23.

4. Set the Compensation Pole Capacitor, C_P.

   Place the compensation pole at the zero produced by the R_ESR and the C_OUT. It is useful for canceling unhelpful effects of the ESR zero.

   Equation 24.
   Equation 25.

   Set ƒ_P2 = ƒ_ESR, and get

   Equation 26.