AD7711ANZ Analog Devices Inc, AD7711ANZ Datasheet - Page 11

• Manufacturer Part Number: AD7711ANZ
• Description: 24 BIT SIGMA DELTA ADC IC
• Manufacturer: Analog Devices Inc

Specifications of AD7711ANZ

• Rohs Compliant: YES
• Number Of Bits: 24
• Sampling Rate (per Second): 1.03k
• Data Interface: Serial
• Number Of Converters: 1
• Power Dissipation (max): 45mW
• Voltage Supply Source: Analog and Digital, Dual ±
• Operating Temperature: -40°C ~ 80°C
• Mounting Type: Through Hole
• Package / Case: 24-DIP (0.300", 7.62mm)
• Resolution (bits): 24bit
• Sampling Rate: 19.5kSPS
• Input Channel Type: Differential, Single Ended
• Supply Voltage Range - Analogue: 5V To 10V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Tables I and II show the output rms noise for some typical
notch and –3 dB frequencies. The numbers given are for the
bipolar input ranges with a V
typical and are generated with an analog input voltage of 0 V.
The output noise from the part comes from two sources. The
first is the electrical noise in the semiconductor devices used in
the implementation of the modulator (device noise). The second
occurs when the analog input signal is converted into the digital
domain adding quantization noise. The device noise is at a low
level and is largely independent of frequency. The quantization
noise starts at an even lower level but rises rapidly with increas-
ing frequency to become the dominant noise source. Conse-
quently, lower filter notch settings (below 60 Hz approximately)
tend to be device-noise dominated while higher notch settings
are dominated by quantization noise. Changing the filter notch
and cutoff frequency in the quantization-noise dominated region
results in a more dramatic improvement in noise performance
than it does in the device-noise dominated region as shown in
Table I. Furthermore, quantization noise is added after the PGA,
so effective resolution is independent of gain for the higher filter
First Notch of
Filter and O/P –3 dB
Data Rate
10 Hz
25 Hz
30 Hz
50 Hz
60 Hz
100 Hz
250 Hz
500 Hz
1 kHz
NOTES
1
2
3
First Notch of
Filter and O/P –3 dB
Data Rate
10 Hz
25 Hz
30 Hz
50 Hz
60 Hz
100 Hz
250 Hz
500 Hz
1 kHz
*Effective resolution is defined as the magnitude of the output rms noise with respect to the input full scale (i.e., 2 ¥ V
REV.G
The default condition (after the internal power-on reset) for the first notch of filter is 60 Hz.
For these filter notch frequencies, the output rms noise is primarily dominated by device noise, and, as a result, is independent of the value of the reference voltage.
For these filter notch frequencies, the output rms noise is dominated by quantization noise, and, as a result, is proportional to the value of the reference voltage.
Therefore, increasing the reference voltage will give an increase in the effective resolution of the device (that is, the ratio of the rms noise to the input full scale is
increased because the output rms noise remains constant as the input full scale increases).
a V
REF
2
2
2
2
2
3
of 2.5 V and resolution numbers are rounded to the nearest 0.5 LSB.
3
3
3
1
Frequency Gain of 1
2.62 Hz
6.55 Hz
7.86 Hz
13.1 Hz
15.72 Hz
26.2 Hz
65.5 Hz
131 Hz
262 Hz
Frequency Gain of 1
2.62 Hz
6.55 Hz
7.86 Hz
13.1 Hz
15.72 Hz
26.2 Hz
65.5 Hz
131 Hz
262 Hz
REF
1.0
1.8
2.5
4.33
5.28
13
130
0.6 ¥ 10
3.1 ¥ 10
22.5
21.5
21
20
20
18.5
15
13
10.5
Table II. Effective Resolution vs. Gain and First Notch Frequency
of 2.5 V. These numbers are
Table I. Output Noise vs. Gain and First Notch Frequency
3
3
Gain of 2
0.78
1.1
1.31
2.06
2.36
6.4
75
0.26 ¥ 10
1.6 ¥ 10
Gain of 2
21.5
21
21
20
20
18.5
15
13
10.5
3
3
Typical Output RMS Noise ( V)
Gain of 4
0.48
0.63
0.84
1.2
1.33
3.7
25
140
0.7 ¥ 10
Effective Resolution
Gain of 4
21.5
21
20.5
20
20
18.5
15.5
13
11
3
–11–
Gain of 8
0.33
0.50
0.57
0.64
0.87
1.8
12
70
0.29 ¥ 10
Gain of 8
21
20
20
20
19.5
18.5
15.5
13
11
notch frequencies. Meanwhile, device noise is added in the PGA
and, therefore, effective resolution suffers a little at high gains
for lower notch frequencies.
At the lower filter notch settings (below 60 Hz), the no missing
codes performance of the device is at the 24-bit level. At the higher
settings, more codes will be missed until at the 1 kHz notch setting,
no missing codes performance is guaranteed only to the 12-bit
level. However, since the effective resolution of the part is 10.5 bits
for this filter notch setting, this no missing codes performance
should be more than adequate for all applications.
The effective resolution of the device is defined as the ratio of the
output rms noise to the input full scale. This does not remain
constant with increasing gain or with increasing bandwidth.
Table II is the same as Table I except that the output is expressed
in terms of effective resolution (the magnitude of the rms noise
with respect to 2 ¥ V
sible to do post filtering on the device to improve the output data
rate for a given –3 dB frequency and also to further reduce the
output noise (see the Digital Filtering section).
*
3
(Bits)
Gain of 16
0.25
0.44
0.46
0.54
0.63
1.1
7.5
35
180
Gain of 16
20.5
19.5
19.5
19
19
18
15.5
13
11
REF
/GAIN, or the input full scale). It is pos-
REF
Gain of 32
0.25
0.41
0.43
0.46
0.62
0.9
4
25
120
Gain of 32 Gain of 64 Gain of 128
19.5
18.5
18.5
18.5
18
17.5
15.5
12.5
10.5
/GAIN). The above table applies for
Gain of 64
0.25
0.38
0.4
0.46
0.6
0.65
2.7
15
70
18.5
17.5
17.5
17.5
17
17
15
12.5
10
AD7711
17.5
16.5
16.5
16.5
16
16
14.5
12.5
10
Gain of 128
0.25
0.38
0.4
0.46
0.56
0.65
1.7
8
40
2