What Is a Mixed Signal Oscilloscope?
A mixed signal oscilloscope is a digital oscilloscope with an analyzer function.
The latest digital oscilloscopes are increasingly equipped with logic input functions and can display both analog and digital signals, which are called mixed signal oscilloscopes, to distinguish them from ordinary oscilloscopes. Mixed signal oscilloscopes display the signal waveform from the analog input channel and the logic waveform from the digital input channel on a single display, allowing the two to be compared on the same time axis.
Uses of Mixed Signal Oscilloscopes
Mixed signal oscilloscopes are used for signal analysis, especially for circuits with mixed analog and digital signals. Conventionally, an oscilloscope is used to observe analog signals and a logic analyzer is used to observe digital signals, and measurements are made by combining these two instruments.
For example, by triggering a digital signal from a logic circuit at the timing when the signal shows a specific status, the signal waveforms of the analog circuit before and after the trigger can be observed. It is also an extremely effective measuring instrument for analyzing troubles that occur at specific timing in high-speed digital circuits, using an oscilloscope to observe the waveform of digital signals to determine if there is a rise time delay or overshooting/undershooting.
Principle of Mixed Signal Oscilloscopes
A mixed signal oscilloscope is a measurement instrument that incorporates the functions of a logic analyzer into a digital oscilloscope, integrating the two to enable acquisition of waveform data. Both functions capture data based on a common time axis, so the timing of analog signal waveforms and digital signals of logic circuits are perfectly matched.
The standard specifications for analog inputs are 4 to 8 channels with 8 to 12 bit resolution, while digital inputs are 16 or more channels and are treated as 1-bit signals. The memory length varies from model to model, but the larger the memory length, the more advantageous it is in terms of measurement. In general, digital signals can acquire data for a longer period.
The analog signal waveform and digital signal are displayed on the display with a common time axis, so the relationship between the two can be clearly seen at a glance, which is very effective for analyzing circuit operation. Some models use an operating system such as Windows 10, which inherits the operability of PCs and tablets, making it possible to work more efficiently.
More About Mixed Signal Oscilloscopes
Useful Features Specific to Mixed Signal Oscilloscopes
The following is an example of a useful feature unique to mixed signal oscilloscopes that can be used to analyze the circuitry of a memory device. The commands output from the controller to memory are defined as a combination of RAS, CAS, and WE signals, and by using symbols instead of signal names, you can display not only “Hi” and “Lo” logic waveforms but also “Read” and “Write” symbols, This is very useful for signal analysis.
Furthermore, by setting a “Read” or “Write” pattern as a trigger condition, you can observe the signal waveforms of the data or address at that time on the oscilloscope. Conversely, if an abnormal waveform input to the oscilloscope is set as the trigger condition, it is possible to check the sequence in which the phenomenon occurs.
Another example is to deal with the shortage of channels in a normal oscilloscope. The extra logic channels cannot be used to observe waveforms, but can be set for trigger input or timing checks. Therefore, the oscilloscope channels can be effectively utilized because they can be assigned only to signals whose waveforms are to be observed.