A Beginner’s Guide To ADC Selection

August 1, 2019

Digital circuitry is largely preferred in signal processing over analog because of its decreased sensitivity to fluctuations in various parameters as voltage, current, etc. and easy integration with computers.

However, there are a few exceptions in the realm of signal conditioning in terms of sensors that operate on analog signals. These sensors are then used with an ADC or Analog-to-Digital Converter that acts as a bridge between the analog and digital domains.

The ADC Process

ADCs convert analog signals into digital by first sampling the incoming signal on either the rising or falling edge of a sample clock. During every cycle, the ADC samples the input analog signal, measures it and approximates it to a digital value with precision.

There are two factors in analog-to-digital conversion that determine the accuracy of the final value. These are the sampling rate and quantization levels.

For accurate signal reconstruction, the sampling rate should be twice of the largest frequency component of the analog signal, according to the Nyquist Theorem.

Selecting An ADC

With a huge variety of ADCs available in the market, selecting the best among them for your project can be a difficult task. Here are a few considerations that you should take into account while selecting an ADC for your project:

ADC Specifications

According to your particular project, find an ADC that closely matches the speed, linearity, resolution, stability and accuracy requirements of your project. Moreover, ensure that the ADC you’re selecting is compatible with the specific model of microprocessor you’re using in your project.

Moreover, select the sampling rate in order to find acquisition speed by using the Nyquist Theorem.

Accuracy And Resolution

Accuracy and resolution are widely confused with one another as they’re closely related. Resolution determines the bit count in the digitized output. It depends on the least input change that increases the digitized output by a single digit. This is associated with the change in the LSB or Least Significant Bit of a converter.

On the other hand, accuracy—also measured in LSB—is determined by the differential and integral nonlinearity of a converter.

Integral nonlinearity shows the difference between the output value of digitized signal and the ideal value. Differential nonlinearity shows the difference in width of the digitized code. Missing of codes can occur if the differential nonlinearity becomes greater than 1 LSB.

To avoid missing of codes, look for ADCs that specify that the differential nonlinearity is not greater than 1 LSB.

ADSANTEC offers a wide variety of 4-bit ADCs for their customers. Browse through our list of available ADCs to find one suitable for your project.

For more information and pricing details, contact us at (310) 530-9400.