2 Analog-to-Digital Converter Error

Understanding voltage reference specifications is necessary to evaluate the right voltage reference for the signal chain application. The main errors affecting the signal chain elements such as an ADC are gain error, noise error, and dynamic error. In ADCs, the gain error is a static error that effects every sample in a continuous sampling period of an ADC and can be reduced or eliminated with calibration. Noise error is an error that affect every sample independently and randomly and is inherent to semiconductor devices and architectures. Examples of noise error are 1/f noise and broadband noise. In ADCs, the noise affects all the measurements and cannot be eliminated but can be attenuated through filtering or by using digital processing techniques. Dynamic error is an error that is caused by fast switching voltage rails or change in load current. This is often associated with the input rails of the ADC but dynamic error also applies to any fast switching on output of the voltage reference. Dynamic error in this document is focused around droop error which is related to the data converter architecture and voltage reference output stage. Gain, noise, and dynamic errors are affected by the voltage reference performance. Table 2-1 covers general guidelines on voltage reference to ADC/DAC pairings but there is still flexibility based on system requirements. The background behind these choices is covered in this document.