Rev 21 Jan 2014 15:09 | Page 14

Figure 12. Output Ripple, V

C

Set the oscilloscope to ac, 10 mV/division, and 2 µs/division time base, with the bandwidth set to 20

MHz to avoid noise interference with the measurements. To minimize coupling, shorten the ground

loop of the oscilloscope probe.

To effectively measure the output voltage ripple, solder a wire to the negative (−) capacitor terminal

and wrap it around the barrel of the probe and connect the tip directly to the positive (+) capacitor

terminal, as shown in Figure 13.

Figure 13. Measuring Output Voltage Ripple

Measuring the Switching Waveform of Buck

To observe the switching waveform with an oscilloscope, place the oscilloscope probe tip at the end of

the inductor with the probe ground at GND. Set the oscilloscope to dc,

5 V/division, and 1 µs/division time base.