This slide shows that higher switching frequencies improve load transient performance because the bandwidth of the controller can be increased. The difference is seen in these two scope images. The image on the left is the LM26420 running at a switching frequency of 2.2MHz. The image on the right is the LM26420 running at a switching frequency of 550KHz. It can be seen that the 550KHz version has approximately 50% more change in output voltage due in part to the lower switching frequency. Note that this is a simple load transient test done in the time-domain. It provides a decent estimate of the overall quality of the loop dynamics, but it is not with 100% certainty that the phase and gain margins remain adequate under all conditions. A more thorough approach is to examine the regulator’s frequency domain behavior through a bode plot. It provides the only way to know for certain if a loop is stable and by how much.