AD7705/AD7706
Table II. Peak-to-Peak Resolution vs. Gain and Output Update Rate @ 5 V
Filter First
Notch and O/P –3 dB
Data Rate
Frequency
MCLK IN = 2.4576 MHz
50 Hz
13.1 Hz
60 Hz
15.72 Hz
250 Hz
65.5 Hz
500 Hz
131 Hz
MCLK IN = 1 MHz
20 Hz
5.24 Hz
25 Hz
6.55 Hz
100 Hz
26.2 Hz
200 Hz
52.4 Hz
Typical Peak-to-Peak Resolution Bits
Gain of
Gain of
Gain of
Gain of
4
8
16
32
16
16
13
10
16
16
13
10
16
16
13
10
16
16
13
10
16
15
13
10
16
15
13
10
16
14
13
10
16
14
13
10
Gain of
1
16
16
13
10
16
16
13
10
Gain of
2
16
16
13
10
16
16
13
10
Gain of
64
15
14
12
10
15
14
12
10
Gain of
128
14
13
12
10
14
13
12
10
OUTPUT NOISE (3 V OPERATION)
Table III shows the AD7705/AD7706 output rms noise for the selectable notch and –3 dB frequencies for the part, as selected by
FS0 and FS1 of the Clock Register. The numbers given are for the bipolar input ranges with a V
REF
of +1.225 V and a V
DD
= 3 V.
These numbers are typical and are generated at an analog input voltage of 0 V with the part used in either buffered or unbuffered
mode. Table II meanwhile shows the output
peak-to-peak
noise for the selectable notch and –3 dB 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 bipolar input ranges with a V
REF
of +1.225 V and for either buffered or unbuffered
mode. These numbers are typical and are rounded to the nearest LSB. The numbers apply for the CLK DIV bit of the Clock Regis-
ter set to 0.
Table III. Output RMS Noise vs. Gain and Output Update Rate @ 3 V
Filter First
Notch and O/P –3 dB
Data Rate
Frequency
MCLK IN = 2.4576 MHz
50 Hz
13.1 Hz
60 Hz
15.72 Hz
250 Hz
65.5 Hz
500 Hz
131 Hz
MCLK IN = 1 MHz
20 Hz
5.24 Hz
25 Hz
6.55 Hz
100 Hz
26.2 Hz
200 Hz
52.4 Hz
Typical Output RMS Noise in V
Gain of
Gain of
Gain of
4
8
16
1.5
1.7
14
65
1.5
1.7
14
65
1.3
1.5
9.9
41
1.3
1.5
9.9
41
1.1
1.2
5.1
22
1.1
1.2
5.1
22
Gain of
1
3.8
5.1
50
270
3.8
5.1
50
270
Gain of
2
2.4
2.9
25
135
2.4
2.9
25
135
Gain of
32
1.0
1.0
2.6
9.7
1.0
1.0
2.6
9.7
Gain of
64
0.9
0.9
2.3
5.1
0.9
0.9
2.3
5.1
Gain of
128
0.9
0.9
2.0
3.3
0.9
0.9
2.0
3.3
Table IV. Peak-to-Peak Resolution vs. Gain and Output Update Rate @ 3 V
Fi
lter First
Notch and O/P –3 dB
Data Rate
Frequency
Gain of
1
16
16
13
10
16
16
13
10
Gain of
2
16
16
13
10
16
16
13
10
Typical Peak-to-Peak Resolution in Bits
Gain of
Gain of
Gain of
Gain of
4
8
16
32
15
15
13
10
15
15
13
10
15
14
13
10
15
14
13
10
14
14
12
10
14
14
12
10
13
13
12
10
13
13
12
10
Gain of
64
13
13
11
10
13
13
11
10
Gain of
128
12
12
11
10
12
12
11
10
M
CLK IN = 2.4576 MHz
50 Hz
13.1 Hz
60 Hz
15.72 Hz
250 Hz
65.5 Hz
500 Hz
131 Hz
MCLK IN = 1 MHz
20 Hz
5.24 Hz
25 Hz
6.55 Hz
100 Hz
26.2 Hz
200 Hz
52.4 Hz
–8–
REV. A
AD [ ANALOG DEVICES ]
