This is where the resolution comes into the picture. It can’t detect the difference between 1mV and 3mV since both will be detected as 0. This means 4.8mV in the analog pin will be detected as 1 and 9.6mV will be 2 (10 in binary). So for a 5V reference voltage, the minimum voltage will be 5/1024 = 4.8mV. For a 10 bit resolution ADC, it is possible to divide up to 1024 (2^10) voltages. The resolution indicates how much the reference voltage can be divided. The ADC in PIC18F4550 is a successive approximation ADC with a resolution of 10 bits. For example, an ADC with 10-bit resolution as one in PIC 18F4550 can have 2^10 (1024) intervals for the range of analog input signal. The resolution of an n-bit ADC is 1/(2^n). Resolution is nothing but the number of levels or intervals which can be divided from a certain analog input range which is expressed in bits. The performance of the ADC is measured using the resolution and speed as parameters. The digital code corresponding to the analog level is the desired digital representation of the analog signal. The generation is stopped when the analog level becomes larger than the analog signal.
The successive approximation ADC generates a series of digital codes each corresponding to a fixed analog level with an internal counter to compare with the analog signal under conversion.
The most inexpensive ADC available in the electronic market is the successive approximation type. There exist many types of ADCs for different purposes like counter type, flash type, successive approximation type, etc. Analog to digital conversion becomes inevitable when these real-world signals need to be processed in a digital environment.ĪDC is the primary means by which an analog signal is converted into digital data that can be processed easily using a digital computer. Most of the real world signals around us are analog in nature. Analog to Digital ConvertersĪnalog signals are continuous time-varying signals. This chapter describes the functioning of an analog to digital converter using PIC18F4550. Analog to digital converters are electronic devices widely used in today’s digital world as most of the real-time signals are analog ones while the day-to-day devices of the contemporary world are mostly digital devices which can process only digital signals.
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