1 Introduction

Multiple systems ranging from thermostats to flight control employ an analog-to-digital converter (ADC) to capture real world analog signals which will be processed in the digital domain and take necessary actions based off of the digital results. Each ADC specifies a number of bits to represent the various digital levels it can produce. For a given constant ADC input, the output of the ADC is not a constant digital value due to various errors in a typical signal chain. Thus, it is important to consider the effective number of bits (ENOB) or the noise-free resolution of the signal chain for better comparison and to also extract maximum information from the captured data. Higher precision calls for higher ENOB and noise free resolution.

Typically, signal-to-noise ratio (SNR), total harmonic distortion (THD) and noise of the system play an important role in ENOB calculation. For multiple systems like field transmitters or test and measurement applications, DC input signal accuracy and precision is critical. Therefore, the noise specification becomes most critical. The voltage reference used with an ADC is a critical component in the signal chain that can impact the precision and accuracy.