Datasheet

AD7191
Rev. A | Page 13 of 20
RMS NOISE AND RESOLUTION SPECIFICATIONS
Table 5 shows the rms noise of the AD7191 for the four output
data rates and four gains. The numbers given are for an
external 5 V reference. These numbers are typical and are
generated with a differential input voltage of 0 V. Table 6
shows the effective resolution; the output peak-to-peak (p-p)
resolution is listed in brackets. It is important to note that the
effective resolution is calculated using the rms noise, whereas
the p-p resolution is calculated based on peak-to-peak noise.
The p-p resolution represents the resolution for which there is
no code flicker. These numbers are typical and are rounded to
the nearest half-LSB.
The effective resolution (ENOB) is defined as
ENOB = log
2
(Full-Scale Range/rms Noise)
The noise-free bits or p-p resolution is defined as
p-p Resolution = log
2
(Full-Scale Range/p-p Noise)
where Full-Scale Range = 2 × V
REF
/Gain.
Table 5. RMS Noise (nV) vs. Gain and Output Data Rate Using a 5 V Reference
ODR2, ODR1 Output Data Rate (Hz) Settling Time (ms) Gain of 1 Gain of 8 Gain of 64 Gain of 128
11 10 400 490 85 17 15
10 50 80 2000 260 46 34
01 60 66.7 2100 273 48 38
00 120 33.3 2400 315 64 51
Table 6. Typical Resolution (Bits) vs. Gain and Output Update Rate Using a 5 V Reference
ODR2, ODR1 Output Data Rate (Hz) Settling Time (ms) Gain of 1 Gain of 8 Gain of 64 Gain of 128
11 10 400 24 (21.5) 23.5 (21) 23 (20.5) 22 (19.5)
10 50 80 22 (19.5) 22 (19.5) 21.5 (19) 20.5 (18)
01 60 66.7 22 (19.5) 22 (19.5) 21.5 (19) 20.5 (18)
00 120 33.3 22 (19.5) 21.5 (19) 21 (18.5) 20 (17.5)