Datasheet
2
AD7714
REV. C
–13–
BUFFERED MODE NOISE
Table III shows the typical output rms noise and effective resolution for some typical notch and –3␣ dB frequencies for the AD7714-
5 with f
CLK␣ IN
= 2.4576␣ MHz and BUFFER = +5 V. Table IV gives the information for the AD7714-3 again with f
CLK IN
= 2.4576
MHz and BUFFER = +5␣ V. The numbers given are for the bipolar input ranges and are generated with a differential analog input
voltage of 0␣ V. For the AD7714-5, the V
REF
voltage is +2.5␣ V while for the AD7714 the V
REF
voltage is +1.25␣ V. The numbers in
brackets in each table are for the effective resolution of the part (rounded to the nearest 0.5 LSB). The effective resolution of the
device is defined as the ratio of the output rms noise to the input full scale (i.e., 2 × V
REF
/GAIN). It should be noted that it is not
calculated using peak-to-peak output noise numbers. Peak-to-peak noise numbers can be up to 6.6 times the rms numbers while
effective resolution numbers based on peak-to-peak noise can be 2.5 bits below the effective resolution based on rms noise as quoted
in the tables.
Table III. AD7714-5 Buffered Mode Output Noise/Resolution for f
CLK IN
= 2.4576␣ MHz
Filter First
Typical Output RMS Noise in V (Effective Resolution in Bits)
Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of
Data Rate Frequency 1 2 4 8 16 32 64 128
5␣ Hz 1.31␣ Hz 0.99 (22.5) 0.68 (22) 0.46 (21.5) 0.26 (21) 0.26 (20) 0.26 (19) 0.26 (18) 0.26 (17)
10␣ Hz 2.62␣ Hz 1.5 (21.5) 0.95 (21.5) 0.63 (21) 0.41 (20.5) 0.39 (19.5) 0.36 (18.5) 0.36 (17.5) 0.36 (16.5)
25␣ Hz 6.55␣ Hz 2.5 (21) 1.7 (20.5) 0.88 (20.5) 0.75 (19.5) 0.57 (19) 0.57 (18) 0.57 (17) 0.56 (16)
30␣ Hz 7.86␣ Hz 2.9 (20.5) 1.8 (20.5) 1 (20) 0.87 (19.5) 0.75 (18.5) 0.72 (17.5) 0.72 (16.5) 0.71 (15.5)
50␣ Hz 13.1␣ Hz 4.2 (20) 2.5 (20) 1.5 (19.5) 1.1 (19) 0.94 (18.5) 0.94 (17.5) 0.94 (16.5) 0.87 (15.5)
60␣ Hz 15.72␣ Hz 6.1 (19.5) 2.9 (19.5) 2 (19.5) 1.2 (19) 1 (18.5) 0.97 (17.5) 0.95 (16.5) 0.94 (15.5)
100␣ Hz 26.2␣ Hz 13.8 (18.5) 6.5 (18.5) 3.5 (18.5) 2.2 (18) 1.3 (18) 1.2 (17) 1.3 (16) 1.1 (15)
250␣ Hz 65.5␣ Hz 87 (16) 56 (15.5) 25 (15.5) 11 (15.5) 5.7 (15.5) 3.6 (15.5) 2.4 (15) 2.1 (14)
500␣ Hz 131␣ Hz 508 (13.5) 241 (13.5) 117 (13.5) 73 (13) 34 (13) 16 (13) 8.5 (13) 5.2 (13)
1␣ kHz 262␣ Hz 2860 (11) 1700 (10.5) 745 (10.5) 480 (10.5) 197 (10.5) 94 (10.5) 53 (10.5) 23 (10.5)
Table IV. AD7714-3 Buffered Mode Output Noise/Resolution for f
CLK IN
= 2.4576␣ MHz
Filter First
Typical Output RMS Noise in V (Effective Resolution in Bits)
Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of
Data Rate Frequency 1 2 4 8 16 32 64 128
5␣ Hz 1.31␣ Hz 1.16 (21) 0.76 (20.5) 0.34 (20) 0.29 (20) 0.29 (19) 0.28 (18) 0.26 (17) 0.26 (16)
10␣ Hz 2.62␣ Hz 1.7 (20.5) 1 (20.5) 0.7 (20) 0.46 (19.5) 0.45 (18.5) 0.4 (17.5) 0.4 (16.5) 0.4 (15.5)
25␣ Hz 6.55␣ Hz 3.5 (19.5) 1.8 (19.5) 1.1 (19) 0.74 (18.5) 0.63 (18) 0.6 (17) 0.6 (16) 0.6 (15)
30␣ Hz 7.86␣ Hz 3.7 (19.5) 2.2 (19) 1.3 (19) 0.76 (18.5) 0.68 (18) 0.66 (17) 0.66 (16) 0.66 (15)
50␣ Hz 13.1␣ Hz 4.5 (19) 3 (18.5) 1.7 (18.5) 1.0 (18) 0.92 (17.5) 0.9 (16.5) 0.89 (15.5) 0.89 (14.5)
60␣ Hz 15.72␣ Hz 5.3 (19) 3.3 (18.5) 1.8 (18.5) 1.1 (18) 1 (17) 0.96 (16.5) 0.96 (15.5) 0.96 (14.5)
100␣ Hz 26.2␣ Hz 10 (18) 4.9 (18) 3.1 (17.5) 1.5 (17.5) 1.2 (17) 1.2 (16) 1.2 (15) 1.2 (14)
250␣ Hz 65.5␣ Hz 47 (15.5) 29 (15.5) 15 (15.5) 7.5 (15.5) 4.7 (15) 2.6 (15) 2.5 (14) 1.6 (13.5)
500␣ Hz 131␣ Hz 300 (13.5) 171 (13) 74 (13) 35 (13) 21 (13) 8.6 (13) 5.6 (13) 3.1 (12.5)
1␣ kHz 262␣ Hz 1722 (10.5) 735 (10.5) 380 (10.5) 230 (10.5) 93 (10.5) 55 (10.5) 30 (10.5) 12 (10.5)