SNVA991A October 2022 – October 2025 LM5123-Q1
The CHF capacitor sets the high frequency pole of the compensation network. The high frequency pole aids in attenuating high frequency noise due to the switching frequency and assuring enough gain margin. It is recommended to set the pole frequency between the minimum RHP zero (fRHPz) and one-half the switching frequency (fSW). The pole location is set at the geometric mean of the RHP zero and one-half the switching frequency using Equation 27.
The pole of the compensation network is selected to be approximately 65.5 kHz. CHF is calculated using Equation 28.
CHF is estimated to be 44.6 pF. Selecting the nearest standard value, CHF is selected to be 47 pF.