Method and apparatus for predicting transient response of a closed loop apparatus

Abstract

A method for predicting transient response of a closed loop apparatus includes the steps of: (a) providing a first reference tool that relates load-free impedance response with a first design gain-phase variable; (b) providing a second reference tool that relates load-free impedance response with a second design gain-phase variable; (c) determining a combined impedance response as a function of frequency; (d) employing at least one of the first and second reference tool to establish a first design value for one of the phase variable and the design load impedance at a characteristic frequency that occurs at a peak value of the combined impedance response; (e) employing at least one of the first and second reference tool to establish a second design value for the other parameter of the phase variable and the design load impedance at the characteristic frequency; (f) establishing a transient multiplier as a function of frequency associated with the output voltage with the design load impedance for selected values of phase margin; (g) creating a third reference tool relating the transient multiplier with phase margin; (h) employing the third reference tool to establish a third design value for the transient multiplier associated with the characteristic frequency and at least one of the first design and second design value; and (i) mathematically combining at least two of the first, second and third design value with a design step current to establish transient excursion of the output voltage in response to applying the design step current.