Datasheet

AD629
Rev. C | Page 14 of 16
ERROR BUDGET ANALYSIS EXAMPLE 2
This application is similar to the previous example except
that the sensed load current is from an amplifier with an ac
common-mode component of ±100 V (frequency = 500 Hz)
present on the shunt (see Figure 41). All other conditions are
the same as before. Note that the same kind of power-line
interference can happen as detailed in Example 1. However,
the ac common-mode component of 200 V p-p coming from
the shunt is much larger than the interference of 1 V p-p;
therefore, this interference component can be neglected.
REF (–)
OUTPUT
CURRENT
60Hz
POWER LINE
1Ω
SHUNT
REF (+)
–V
S
+V
S
V
OUT
NC
–IN
+IN
0.1µF
0.1µF
NC = NO CONNECT
21.1kΩ
380kΩ 380kΩ
20kΩ
380kΩ
AD629
1
2
3
4
8
7
6
5
00783-039
10 AMPS
±100V AC CM
TO GROUND
Figure 41. Error Budget Analysis Example 2: V
IN
= 10 V Full-Scale,
V
CM
= ±100 V at 500 Hz, R
SHUNT
=1 Ω
Table 8. AD629 vs. INA117 AC Error Budget Example 2 (V
CM
= ±100 V @ 500 Hz)
Error, ppm of FS
Error Source AD629 INA117 AD629 INA117
ACCURACY, T
A
= 25°C
Initial Gain Error (0.0005 × 10)/10 V × 10
6
(0.0005 × 10)/10 V × 10
6
500 500
Offset Voltage (0.001 V/10 V) × 10
6
(0.002 V/10 V) × 10
6
100 200
Total Accuracy Error
600 700
TEMPERATURE DRIFT (85°C)
Gain 10 ppm/°C × 60°C 10 ppm/°C × 60°C 600 600
Offset Voltage (20 μV/°C × 60°C) × 10
6
/10 V (40 μV/°C × 60°C) × 10
6
/10 V 120 240
Total Drift Error
720 840
RESOLUTION
Noise, Typical, 0.01 Hz to 10 Hz, μV p-p 15 μV/10 V × 10
6
25 μV/10 V × 10
6
2 3
CMR, 60 Hz (141 × 10
-6
× 1 V)/10 V × 10
6
(500 × 10
-6
× 1 V)/10 V × 10
6
14 50
Nonlinearity (10
-5
× 10 V)/10 V × 10
6
(10
-5
× 10 V)/10 V × 10
6
10 10
AC CMR @ 500 Hz (141 × 10
-6
× 200 V)/10 V × 10
6
(500 × 10
-6
× 200 V)/10 V × 10
6
2820 10,000
Total Resolution Error
2846 10,063
Total Error
4166 11,603