Digital scope

On a digital scope such as the TDS420/460 series, you may want to set it to display the waveform on average setting (maybe 10-20 waveforms superimposed), instead of the high-res or sample capture modes. It will create a fuzz similar to an analog scope. 

Now you can clearly distinguish between clock instability and excessive (trailing edge) jitter. Remember, also, that you can set a digital scope to report the frequency of the waveform. Watch that number closely and make sure it is quite stable, otherwise you have clock instability. 

This is probably the best feature of digital scopes when it comes to troubleshooting switching power supplies. This is where they win hands down against analog scopes. This mode can be used to capture non-repetitive events such as... 

A detailed block diagram of a basic DSO is shown in Fig. 20.60. The features included in this design are typical of a digital scope. The major circuit blocks are... 

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