7.1 Test Setup for Graphs

To capture the graphs displayed in the Typical Characteristics section, the following first-order RC-filter setup was used with the exception of the waveform in Figure 15 which was captured without any output filter. The filter should be used when viewing output signals on an oscilloscope because output PWM modulation is present in all modes. Ensure that effective impedance of the filter is not too low because the closed-loop and auto resonance-tracking features can be affected. Therefore, TI recommends that this exact filter be used for output measurement. Most oscilloscopes have an input impedance of 1 MΩ on each channel and therefore have an approximately 1% loss in measured amplitude because of the voltage-divider effect with the filter.

Figure 15. Test Setup