The resolution determines amplitude precision and rounding error (and thus the quantization noise and a baseline loss of accuracy). High-speed internet scenarios such as cable modems, xDSL, etc.Īs for accuracy, it results from the combination of resolution and sampling speed. Pipeline designs are essentially a more refined version of the SAR, and they are well-suited to a wide range of applications, including: As a result, you’ll see delta-sigma designs employed largely for digital audio and instrumentation.įinally, pipelined ADCs are becoming more and more popular due to their ability to combine both reasonably high resolution and speeds. In these instances, capturing even small nuances is critical, but total amount of data isn’t extreme (compared to video, for example). SARs are very popular in data-acquisition and instrumentation applications, where ultra-high speed is less critical, and accuracy reigns supreme.ĭelta-sigma architecture (one of the newest designs) can boast astounding accuracy, but it’s also the slowest of the popular designs, making it well-suited to high-fidelity audio applications. While flash ADCs are large and expensive, their speed makes them quality candidates for converting analog video recording to digital, a process that deals with huge amounts of data. Pipelined ADCs, however, are a somewhat unique method: they combine some of the best qualities of SARs and flash-type ADCs, managing to achieve both high speed and high resolution. A clear idea of what you want your device to achieve will help you prioritize the four factors we described above and guide you toward the right type of ADC architecture.įor a given architecture type, the higher an ADC’s resolution is, the lower its speed will be (and vice versa), since higher resolution means more data to convert.
As a result, your project and intended use case will largely dictate which type of ADC you choose to use. The various ADC designs have their own strengths and weaknesses. With high enough resolution, it is possible to overcome quantizing noise functionally, but it remains an inherent part of the ADC process. We refer to that lost information as quantizing noise, and it manifests as a sawtooth noise signal.
Simply put, when a continuous set converts to a discrete set, we can expect to lose some information. This type of noise deserves its own mention because quantizing noise is unavoidable in analog-to-digital conversion. Quantization noise is one of several noise types that contribute to the device’s accuracy. Higher resolution generally leads to higher accuracy as well, since the smaller the rounding error, the more true the digital output is to the analog input. Even in an ideal ADC, there will be some amount of noise present since rounding must necessarily occur in order to digitize an analog signal (quantization noise, explained below). How closely does the output match the input? How much of the output is the desired signal? Generally, we assess accuracy in terms of the noise present in the output signal, using a figure called the signal-to-noise ratio (SNR), where higher is better (more signal per given amount of noise). That figure determines how many samples per second are possible in a best-case scenario.Īccuracy is relatively straightforward. Speed has to do with the device’s sampling rate – in other words, what is the highest number of conversions per second that the ADC can handle? Sampling rate is determined by how much time it takes to perform a single conversion. Resolution also defines the smallest incremental change to the analog signal that the ADC can express. This figure determines the smallest input signal that the system can represent.
Resolution refers to the number of output bits that the ADC can generate per conversion. Once you’ve assessed your project’s needs in those areas, you can narrow your selection even more by considering less important variables, such as:Īs you explore the world of ADCs, it may be helpful to refresh your memory on how resolution, speed, accuracy, and noise will affect your choice.
To select the right ADC, you’ll first need to consider four critical factors:
0 kommentar(er)
