
REV. C
AD7715
–12–
OUTPUT NOISE
AD7715-5
Table V shows the AD7715-5 output rms noise for the selectable notch and –3dB frequencies for the part, as selected by FS1 and
FS0 of the Setup Register. The numbers given are for the bipolar input ranges with a V
REF
of +2.5V. These numbers are typical
and are generated at a differential analog input voltage of 0V with the part used in unbuffered mode (BUF bit of the Setup Register
= 0). Table VI meanwhile shows the output
peak-to-peak
noise for the selectable notch and –3dB frequencies for the part.
It is im-
portant to note that these numbers represent the resolution for which there will be no code flicker. They are not calculated based on rms noise but
on peak-to-peak noise
. The numbers given are for the bipolar input ranges with a V
REF
of +2.5V and for the BUF bit of the Setup
Register = 0. These numbers are typical, are generated at an analog input voltage of 0V and are rounded to the nearest LSB.
Meanwhile, Table VII and Table VIII show rms noise and peak-to-peak resolution respectively with the AD7715-5 operating under
the same conditions as above except that now the part is operating in buffered mode (BUF Bit of the Setup Register = 1).
Table V. Output RMS Noise vs. Gain and Output Update Rate for AD7715-5 (Unbuffered Mode)
Filter First Notch & O/P Data Rate
–3dB Frequency
Typical Output RMS Noise in
m
V
MCLK IN =
2.4576 MHz
50Hz
60Hz
250Hz
500Hz
MCLK IN =
1 MHz
20Hz
25Hz
100Hz
200Hz
MCLK IN =
2.4576 MHz
13.1Hz
15.72Hz
65.5Hz
131Hz
MCLK IN =
1 MHz
5.24Hz
6.55Hz
26.2Hz
52.4Hz
GAIN = 1
3.8
4.8
103
530
GAIN = 2
1.9
2.4
45
250
GAIN = 32
0.6
0.6
3.0
18
GAIN = 128
0.52
0.62
1.6
5.5
Table VI. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-5 (Unbuffered Mode)
Filter First Notch & O/P Data Rate
–3dB Frequency
Typical Peak-to-Peak Resolution in Bits
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
GAIN = 1
GAIN = 2
GAIN = 32
GAIN = 128
50Hz
60Hz
250Hz
500Hz
20Hz
25Hz
100Hz
200Hz
13.1Hz
15.72Hz
65.5Hz
131Hz
5.24Hz
6.55Hz
26.2Hz
52.4Hz
16
16
13
10
16
16
13
10
16
16
13
10
14
13
12
10
Table VII. Output RMS Noise vs. Gain and Output Update Rate for AD7715-5 (Buffered Mode)
Filter First Notch & O/P Data Rate
–3dB Frequency
Typical Output RMS Noise in
m
V
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
GAIN = 1
GAIN = 2
GAIN = 32
GAIN = 128
50Hz
60Hz
250Hz
500Hz
20Hz
25Hz
100Hz
200Hz
13.1Hz
15.72Hz
65.5Hz
131Hz
5.24Hz
6.55Hz
26.2Hz
52.4Hz
4.3
5.1
103
550
2.2
3.1
50
280
0.9
1.0
3.9
18
0.9
1.0
2.1
6
Table VIII. Peak-to-Peak Resolution vs. Gain and Output Update Rate for AD7715-5 (Buffered Mode)
Filter First Notch & O/P Data Rate
–3dB Frequency
Typical Peak-to-Peak Resolution in Bits
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
MCLK IN =
2.4576 MHz
MCLK IN =
1 MHz
GAIN = 1
GAIN = 2
GAIN = 32
GAIN = 128
50Hz
60Hz
250Hz
500Hz
20Hz
25Hz
100Hz
200Hz
13.1Hz
15.72Hz
65.5Hz
131Hz
5.24Hz
6.55Hz
26.2Hz
52.4Hz
16
16
13
10
16
16
13
10
15
15
13
10
13
13
12
10