The TPS61379-Q1 uses the fixed frequency peak current mode control. There is an internal adaptive slope compensation to avoid the subharmonic oscillation. With the inductor current information sensed, the small-signal model of the power stage reduces from a two-pole system, created by L and C_OUT, to a single-pole system, created by R_OUT and C_OUT. The single-pole system is easily used with the loop compensation. Figure 9-2 shows the equivalent small signal elements of a boost converter.

The small signal of power stage is:

Equation 13.

where

• D is the duty cycle
• R_OUT is the output load resistor
• R_SENSE is the equivalent internal current sense resistor, which is typically 118 mΩ

The single pole of the power stage is:

Equation 14.

where

• C_OUT is the output capacitance. For a boost converter having multiple, identical output capacitors in parallel, simply combine the capacitors with the equivalent capacitance

The zero created by the ESR of the output capacitor is:

Equation 15.

where

• R_ESR is the equivalent resistance in series of the output capacitor

The right-hand plane zero is:

Equation 16.

where

• D is the duty cycle
• R_OUT is the output load resistor
• L is the inductance

Equation 17 shows the equation for feedback resistor network and the error amplifier.

Equation 17.

where

• R_EA is the output impedance of the error amplifier and typical R_EA = 500 MΩ.
• ƒ_P1, ƒ_P2 is the pole's frequency of the compensation, f_Z is the zero’s frequency of the compensation network

Equation 18.

where

• C_C is the zero capacitor compensation

Equation 19.

where

• C_P is the pole capacitor compensation
• R_C is the resistor of the compensation network

Equation 20.