5 Conclusions

In Part 1, we conclude that loop saturation is so crucial when calculating load transient response. For a fixed design, it is the nature output response of linear system G_{ii_CL}(s), but not load step itself, will determine loop saturation. In D-CAP+ multiphase solution, maximum slew rate of I_sum is limited by voltage, inductance, phase number, switching frequency and blanking time(upwards).

If I_sum maximum slew rate can follow the linear system G_{ii_CL}(s) output nature response, loop saturation never comes. Loop bandwidth becomes the most critical factor coming into picture; If not, loop saturation occurs with more undershoot and overshoot expected. Then everything physical comes into picture except load transient slew rate, others like phase number, blanking time and switching frequency(t_on related) will make impacts.

Part 2 will describe capacitors selection (including types and value) to meet the requirements of output impendence and high rate repetitive load transient.