Digital Converter Dynamic Range

Digital converters are quoted as being 16bit, 20bit, 24bit etc. This is really what number of bits they accept as an input signal rather than the number of bits they are working with internally to do the conversion. The table below shows the signal levels for various bit depths. It is interesting to note that quoted dynamic range for ADCs and DACs seems to fall in line with reduced bit depths. e.g. the ADAV801 ADC has a dynamic range of 102dB which suggests that it is only a 17bit device. Where as the AD1955 and CS5381 are quoted as 120dB - 20bit devices? The data sheets can tell you more than you might think but it is well hidden.