One of the best ways to test the stability and robustness of any design is to perform load transient testing. The circuit shown in Figure 4-3 can be used with the IBB. The PFET is used as a source follower, allowing the load pulse parameters to be set by the pulse generator. This arrangement allows the pulse generator ground to be the same as the system ground. With this method both the load current amplitude and the slew rate of the current pulse are under the control of the pulse generator. The pulse generator amplitude is adjusted to give the desired load current pulse magnitude. Measure the output voltage transient near the terminals of the output capacitor. Size the PFET and R based on the required load current. A value of R = 0.1 Ω is convenient for load currents in the range of 1 A to 3 A. The power dissipation in the PFET must be checked, especially at higher output voltages and loads.

Figure 4-3 Set-up for Measuring Load Transient Response for an IBB