Calculate Settling Time with Signal Browser

This example shows how to use the Bilevel Measurements panel in the SPTool Signal Browser to find the settling time of a clock signal.

First, open SPTool by typing the following at the MATLAB® command line.

sptool

SPTool opens.

In this example, you import a clock signal from the MAT-file named clockex.mat. In the SPTool menu, select File > Import. Alternatively, you can press the Ctrl+I keyboard shortcut. The Import to SPTool dialog box opens.

  1. Under Source, click From Disk.

  2. In the MAT-file box, type clockex, and press Enter. The variables x and t appear under File Contents.

  3. Under File Contents, click x. Click the right arrow ( ) button to the left of the Data box.

  4. In the Sampling Frequency box, type 4000000.

  5. In the Name box, type Clock.

  6. Click OK. The SPTool Signals list now contains a signal named Clock [vector].

  7. In SPTool, in the Signals list, select Clock [vector], and click the View button. The Signal Browser appears and displays the clock signal.

Because you selected only one signal, the legend is not needed. Turn off the legend by clicking the Show All Legends ( ) button. Then, use the Style dialog box to modify the appearance of the axes and the lines for the signal. In the Signal Browser menu, select View > Style.

ParameterDisplay 1 Setting
Axes background colorBlack
Ticks, labels, and grid colorsDark Gray
Line colorYellow

To show the Bilevel Measurements panel, in the Signal Browser menu, select Tools > Measurements > Bilevel Measurements. To collapse the Transitions pane, click the pane collapse button ( ) next to that label. To expand the Settings pane and the Overshoots / Undershoots pane, click the pane expand button ( ) next to each label. The Signal Browser appears as shown in the following figure.

The value for the rising edge Settling Time parameter does not appear in the Overshoots / Undershoots pane because the Settle Seek parameter is too large. The Settle Seek value is longer than the entire simulation duration. Enter a value for settle seek of 2e-6, and press Enter. Signal Browser now displays a rising edge settling time value of 118.392 ns.

This settling time value displayed is actually the statistical average of the settling times for all five rising edges. To display the settling time for only one rising edge, you can zoom in on that transition. In the Signal Browser toolbar, click the Zoom X button ( ). Click the display near a value of 2 microseconds on the time-axis. Drag to the right, and release near a value of 4 microseconds on the time-axis. Signal Browser updates the rising edge Settling Time value to reflect the new time window, as shown in the following figure.

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