Analog-to-Digital Converters

This chapter primarily describes analog-to-digital converters (ADCs) in addition to focusing on digital-to-analog converters (DACs) that can help one understand how ADCs work. The usual method of bringing analog inputs into a microprocessor is to use an ADC. An ADC accepts an analog input, a voltage or a current, and converts it to a digital word that can be read by a microprocessor. The resolution of an ADC is determined by the reference input and the word width. The resolution defines the smallest voltage change that can be measured by the ADC. The tracking ADC has a comparator, a counter, and a digital-to-analog converter. The comparator compares the input voltage to the DAC output voltage. If the input is higher than the DAC voltage, the counter counts up. If the input is lower than the DAC voltage, the counter counts down. The counter counts up once for every clock pulse, stepping the DAC output voltage up. When the counter passes the binary value that represents the input voltage, the comparator output will switch and the counter will count down.