Hello experts,
The datasheet for the ADP7142 linear regulator recommends a minimum 2.2uF output capacitor with ESR<0.3 ohm (see pages 4 and 14): "The ESR of the output capacitor affects the stability of the LDO control loop. A minimum of 2.2 µF capacitance with an ESR of 0.3 Ω or less is recommended to ensure the stability of the ADP7142."
The evaluation board for the ADP7142 uses a 4.7uF 50V Samsung CL31B475KBHNNNE. This has a sufficiently low ESR down to about 10kHz, but the ESR then rises rapidly to about 4 ohms at 100Hz (see data tool, double-click capacitor entry and click R to plot ESR).
I am intending to feed my ADP7142 with a linear supply which will have some minor 100Hz content (and harmonics). Do I need to use a capacitor with lower ESR at 100Hz, or is the stability issue only an issue with higher frequencies?