AD629(RevA) 데이터 시트보기 (PDF) - Analog Devices
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AD629 Datasheet PDF : 12 Pages
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AD629
Output Current and Buffering
The AD629 is designed to drive loads of 2 kΩ to within 2 V of
the rails, but can deliver higher output currents at lower output
voltages (see Figure 15). If higher output current is required,
the AD629’s output should be buffered with a precision op
amp such as the OP113 as shown in Figure 35. This op amp
can swing to within 1 V of either rail while driving a load as
small as 600 Ω.
REF(–) 21.1k⍀ AD629
1
8 NC
380k⍀ 380k⍀
0.1F
–IN
2
7
+IN
–VS
0.1F
380k⍀
3
20k⍀
4
6
REF(+)
5
NC = NO CONNECT
+VS
0.1F
OP113
0.1F
–VS
VOUT
Figure 35. Output Buffering Application
A Gain of 19 Differential Amplifier
While low level signals can be connected directly to the –IN and
+IN inputs of the AD629, differential input signals can also be
connected as shown in Figure 36 to give a precise gain of 19.
However, large common-mode voltages are no longer permissible.
Cold junction compensation can be implemented using a tempera-
ture sensor such as the AD590.
THERMOCOUPLE
+VS
REF(–) 21.1k⍀ AD629
1
8 NC
–IN 380k⍀ 380k⍀
2
7
0.1F
VREF
+IN 380k⍀
3
20k⍀
4
6
REF(+)
5
VOUT
NC = NO CONNECT
Figure 36. A Gain of 19 Thermocouple Amplifier
Error Budget Analysis Example 1
In the dc application below, the 10 A output current from a
device with a high common-mode voltage (such as a power sup-
ply or current-mode amplifier) is sensed across a 1 Ω shunt
resistor (Figure 37). The common-mode voltage is 200 V, and
the resistor terminals are connected through a long pair of lead
wires located in a high-noise environment, for example, 50 Hz/
60 Hz 440 V ac power lines. The calculations in Table III
assume an induced noise level of 1 V at 60 Hz on the leads, in
addition to a full-scale dc differential voltage of 10 V. The error
budget table quantifies the contribution of each error source.
Note that the dominant error source in this example is due to
the dc common-mode voltage.
Table III. AD629 vs. INA117 Error Budget Analysis Example 1 (VCM = 200 V dc)
Error Source
AD629
INA117
Error, ppm of FS
AD629
INA117
ACCURACY, TA = 25°C
Initial Gain Error
Offset Voltage
DC CMR (Over Temperature)
(0.0005 × 10) ÷ 10 V × 106
(0.0005 × 10) ÷ 10 V × 106
(0.001 V ÷ 10 V) × 106
(0.002 V ÷ 10 V) × 106
(224 × 10-6 × 200 V) ÷ 10 V × 106 (500 × 10-6 × 200 V) ÷ 10 V × 106
500
100
4,480
500
200
10,000
Total Accuracy Error: 5,080
10,700
TEMPERATURE DRIFT (85°C)
Gain
10 ppm/°C × 60°C
10 ppm/°C × 60°C
600
600
Offset Voltage
(20 µV/°C × 60°C) × 106/10 V (40 µV/°C × 60°C) × 106/10 V
120
240
Total Drift Error: 720
840
RESOLUTION
Noise, Typ, 0.01–10 Hz, µV p-p 15 µV ÷ 10 V × 106
25 µV ÷ 10 V × 106
2
3
CMR, 60 Hz
(141 × 10–6 × 1 V) ÷ 10 V × 106 (500 × 10–6 × 1 V) ÷ 10 V × 106
14
50
Nonlinearity
(10–5 × 10 V) ÷ 10 V × 106
(10–5 × 10 V) ÷ 10 V × 106
10
10
Total Resolution Error: 26
63
Total Error: 5,826
11,603
–10–
REV. A
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