The loop response of the TPS621x0EVM-627 can be measured with two simple changes to the circuitry. First, install a 10-Ω resistor across the pads in the middle of the back of the PCB. The pads are spaced to allow installation of 0805- or 0603-sized resistors. Second, cut the short section of trace between the via on the output voltage and the trace that connects to the VOS pin via. These changes are shown in Figure 1-1. With these changes, an ac signal (10-mV, peak-to-peak amplitude recommended) can be injected into the control loop across the added resistor.

Figure 1-1 Loop Response Measurement Modification