AD629BRZ(RevC) View Datasheet(PDF) - Analog Devices
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Description
Manufacturer
AD629BRZ Datasheet PDF : 16 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 17). If higher output current is required, the
output of the AD629 should be buffered with a precision op amp,
such as the OP113, as shown in Figure 38. This op amp can swing
to within 1 V of either rail while driving a load as small as 600 Ω.
REF (–) 21.1kΩ AD629
+VS
1
8 NC
–IN
+IN
–VS
380kΩ 380kΩ
2
7
0.1µF
380kΩ
3
20kΩ
4
6
REF (+)
5
0.1µF
OP113
0.1µF
VOUT
0.1µF
NC = NO CONNECT
–VS
Figure 38. 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 39, to give a precise gain of 19.
However, large common-mode voltages are no longer permissible.
Cold junction compensation can be implemented using a
temperature sensor, such as the AD590.
REF (–) 21.1kΩ AD629
+VS
1
8 NC
THERMOCOUPLE
–IN 380kΩ 380kΩ
2
VREF
+IN 380kΩ
3
4
20kΩ
7
+VS
0.1µF
6
VOUT
REF (+)
5
ERROR BUDGET ANALYSIS EXAMPLE 1
In the dc application that follows, the 10 A output current from
a device with a high common-mode voltage (such as a power
supply or current-mode amplifier) is sensed across a 1 Ω shunt
resistor (see Figure 40). 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 7
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.
OUTPUT
CURRENT
10 AMPS
200VCMDC
TO GROUND
1Ω
SHUNT
REF (–) 21.1kΩ AD629
1
8 NC
–IN 380kΩ 380kΩ
2
7
+IN 380kΩ
3
6
+VS
0.1µF
VOUT
–VS
60Hz
POWER LINE
20kΩ
REF (+)
4
5
0.1µF
NC = NO CONNECT
Figure 40. Error Budget Analysis Example 1: VIN = 10 V Full-Scale,
VCM = 200 V DC, RSHUNT = 1 Ω, 1 V p-p, 60 Hz Power-Line Interference
NC = NO CONNECT
Figure 39. A Gain of 19 Thermocouple Amplifier
Table 7. AD629 vs. INA117 Error Budget Analysis Example 1 (VCM = 200 V dc)
Error Source
ACCURACY, TA = 25°C
Initial Gain Error
Offset Voltage
DC CMR (Over Temperature)
TEMPERATURE DRIFT (85°C)
Gain
Offset Voltage
RESOLUTION
Noise, Typical, 0.01 Hz to 10 Hz, μV p-p
CMR, 60 Hz
Nonlinearity
AD629
(0.0005 × 10)/10 V × 106
(0.001 V/10 V) × 106
(224 × 10-6 × 200 V)/10 V × 106
10 ppm/°C × 60°C
(20 μV/°C × 60°C) × 106/10 V
15 μV/10 V × 106
(141 × 10-6 × 1 V)/10 V × 106
(10-5 × 10 V)/10 V × 106
INA117
(0.0005 × 10)/10 V × 106
(0.002 V/10 V) × 106
(500 × 10-6 × 200 V)/10 V × 106
Total Accuracy Error
10 ppm/°C × 60°C
(40 μV/°C × 60°C) × 106/10 V
Total Drift Error
25 μV/10 V × 106
(500 × 10-6 × 1 V)/10 V × 106
(10-5 × 10 V)/10 V × 106
Total Resolution Error
Total Error
Error, ppm of FS
AD629 INA117
500
100
4480
5080
500
200
10,000
10,700
600
600
120
240
720
840
2
14
10
26
5826
3
50
10
63
11,603
Rev. C | Page 13 of 16
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