8-bit ADC

EE 76 July/August 1986 1508-bit ADC Before any analogue voltage can be measured and subsequently pro- cessed by a computer, a converter device with the necessary precision is required to provide the computer with the digital n-bit equivalent of the voltage as applied to the DAC circuit. Obviously, the higher n, the more steps involved in the conversion pro- cess, but also the higher the accu- racy that can be obtained. This 8-bit ADC circuit works with very few parts; yet it is versatile, fast, and sufficiently accurate for most purposes. The maximum input volt- age to the circuit is arranged at 5V, as determined by the resistor network connected to the Am terminal of the Type ZN427 ADC chip. Given this up- per limit for Vi., the conversion ac- curacy equals 5V/(28-1)=19.6mV/step. Other input voltage levels may be ac- commodated by appropriate re- dimensioning of the input voltage divider. Since the proposed ADC chip features an analogue-to-digital con- version time of only lOps (...