For this design, Type 2A compensation was used. With a target crossover frequency of 10 kHz, the guidelines shown in Section 8.3.18 are used here to determine the compensation values needed for the compensation network. The power stage transconductance is first needed in order to calculate the frequency compensation component values.
With the power stage transconductance calculated as 16.2 A/V, the values of the external components needed at the COMP pin can be resolved.
For the output capacitance 7 × 330-μF polymer tantalum capacitors were used to meet the 2.3-mF value that was needed for the design. At the selected switching frequency and output voltage, each of these capacitors had an ESR of roughly 6 mΩ. As such, the equivalent ESR used to determine the frequency of the ESR zero in the frequency response is equivalent the parallel resistance of these seven capacitors, which is 0.86 mΩ. The ESR zero frequency is then used in the calculation of CHF.
The values of RCOMP, CCOMP, and CHF selected were 40.2 kΩ, 15 nF, and 47 pF, respectively. Note that like many other aspects of the design, the frequency compensation is often tuned during testing in order to obtain the best possible performance.