Data Sheet
AD7171
OUTPUT NOISE AND RESOLUTION SPECIFICATIONS
Table 7 shows the rms noise of the AD7171. The numbers
given are for a 5 V and a 3 V reference. These numbers are
typical and are generated with a differential input voltage of 0 V.
The corresponding p-p resolution is also listed along with the
effective resolution (ENOB). Note that the effective resolution is
calculated using the rms noise, whereas the p-p resolution is based
on the p-p noise. The p-p resolution represents the resolution
for which there is no code flicker. These numbers are typical.
The effective number of bits (ENOB) is defined as
The noise-free bits, or p-p resolution, are defined as
Noise-Free Bits = ln(FSR/Peak-to-Peak Noise)/ln(2)
where FSR is the full-scale range and is equal to 2 × VREF/gain.
Table 7. RMS Noise and Resolution of the AD7171
VREF = VDD RMS Noise P-P Noise P-P Resolution
5V
11.5 μV
76 μV
16 bits
3V
6.9 μV
45 μV
16 bits
ENOB
16 bits
16 bits
ENOB = ln(FSR/RMS noise)/ln(2)
Rev. C | Page 9 of 16