Now that the basic simulation has shown that the simulation is fundamentally working, sweeps can be performed to refine the R_s component selection.

To perform a sweep, click on the sweep button, then click on the V_cont voltage source (which controls the value of R_s).

This will bring up a dialog box. Select the "..." button next to the Voltage [V] parameter and configure the sweep to select 5 points on a linear scale from 13 Ω to 138 Ω as shown in Figure 3-8.

The output of the transient simulation with a sweep of R_s is shown in Figure 3-9. Note that the outputs have again been separated, and all outputs other than V_pin and V_error have been deleted. V_error range has been set to -50 mV to +50 mV and the waveform has been limited to better observe the settling.

From this output, it can be concluded:

• Higher resistance values in the R_s range do not provide quick enough settling. For instance, 106 Ω only settles to 6.6 mV in the allocated S+H time while the settling target is 366 µV
• A good range for further investigation would be 10 Ω to 50 Ω

Figure 3-10 shows the results of a sweep of R_s from 10 Ω to 50 Ω. From this set of waveforms, it appears that values of Rs from 10 Ω to 30 Ω all provide settling that greatly exceeds the design target. A final value of R_s was thus selected as 27 Ω.