ADC Analog-to-digital Converter working principle and classification

Now the software, radio, digital Image acquisition requires a high-speed A/d sampling to ensure the effectiveness and accuracy, the general measurement and control system also hopes to have a breakthrough in precision, the tide of human digitalization to promote A/D converter constant change, and A/D converter is the pioneer of digital human realization. A/D converter has been developed for more than more than 30 years and has undergone several technological innovations, ranging from parallel, successive approximation and integral ADC to the newly developed ∑-δ and pipelined ADC in recent years, each of which has its advantages and disadvantages and can be used in different application situations. How the ADC works

A/D converter, or ADC, is usually referred to as an electronic component that converts analog signals into digital signals. A typical analog-to-digital converter is a converter that converts a simulated amount after a comparison with a standard amount to a discrete signal expressed as a binary value. Therefore, any analog-to-digital converter needs a reference analog quantity as the standard of conversion, the most common reference standard is the maximum convertible signal size. The output number indicates the size of the input signal relative to the reference signal. Classification of ADC

There are many kinds of analog-to-digital converters, which can be divided into indirect ADC and direct ADC according to the working principle. The indirect ADC is to convert the input analog voltage to the time or frequency, and then convert these intermediate quantities into digital quantities, which are commonly used with double integral ADC. Direct ADC is directly converted to digital, commonly used parallel ADC and successive approximation type ADC.

　　Parallel comparison ADC: Each of the different levels of parallel comparison, the output code is also produced in parallel, so the conversion speed quickly. The disadvantage of parallel comparator ADC is high cost and large power consumption.

　　successive approximation ADC: It produces a series of comparison voltage VR, but it is generated by the comparison voltage, successive and the input voltage respectively, in order to gradually approximate the mode of analog-to-digital conversion. It is slower than the parallel ADC and is much faster than the dual-scale ADC, and belongs to the medium-speed ADC device.

Dual-Integral ADC : It first carries out two integrals of the input sampling voltage and the reference voltage, obtains the time interval proportional to the average of the sampled voltage, and counts the standard clock pulses with the counter. Its advantages are strong anti-interference ability, good stability; The main disadvantage is that the conversion speed is low ADC selection (Technical specification) Sampling Accuracy ----------------resolution, generally 8-bit, 10-bit, 12-bit, 16-bit, etc. conversion Time -that is, the time required to sample each time, the ADC's conversion speed, the ADC's clock frequency, sampling period, conversion cycle, data output -such as the output of the same port, serial output; ADC Type --as mentioned above, there are several types of ADC, different types of ADC have different performance limits, working voltage --need to pay attention to the operating voltage range of ADC, can directly measure the negative voltage, etc. chip Encapsulation --whether the chip package conforms to the product design requirements; price/Performance --control cost.