AD629
ERROR BUDGET ANALYSIS EXAMPLE 2
OUTPUT
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 ±177 ꢁ (frequency = ±77 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 277 ꢁ p-p coming from
the shunt is much larger than the interference of 1 ꢁ p-p;
therefore, this interference component can be neglected.
CURRENT
AD629
REF (–)
21.1kΩ
10 AMPS
±100V AC CM
TO GROUND
NC
1
2
3
4
8
7
6
5
380kΩ 380kΩ
–IN
+IN
+V
S
0.1µF
1Ω
SHUNT
380kΩ
V
OUT
20kΩ
REF (+)
–V
S
60Hz
0.1µF
POWER LINE
NC = NO CONNECT
Figure 41. Error Budget Analysis Example 2: VIN = 10 V Full-Scale,
VCM 100 V at 500 Hz, RSHUNT =1 Ω
=
Table 8. AD629 vs. INA117 AC Error Budget Example 2 (VCM
=
100 V @ 500 Hz)
INA117
Error, ppm of FS
Error Source
AD629
AD629
INA117
ACCURACY, TA = 25°C
Initial Gain Error
Offset Voltage
(ꢀ.ꢀꢀꢀ5 × 1ꢀ)/1ꢀ V × 1ꢀ6
(ꢀ.ꢀꢀ1 V/1ꢀ V) × 1ꢀ6
(ꢀ.ꢀꢀꢀ5 × 1ꢀ)/1ꢀ V × 1ꢀ6
(ꢀ.ꢀꢀ2 V/1ꢀ V) × 1ꢀ6
5ꢀꢀ
1ꢀꢀ
6ꢀꢀ
5ꢀꢀ
2ꢀꢀ
7ꢀꢀ
Total Accuracy Error
TEMPERATURE DRIFT (85°C)
Gain
1ꢀ ppm/°C × 6ꢀ°C
(2ꢀ μV/°C × 6ꢀ°C) × 1ꢀ6/1ꢀ V
1ꢀ ppm/°C × 6ꢀ°C
6ꢀꢀ
12ꢀ
72ꢀ
6ꢀꢀ
24ꢀ
84ꢀ
Offset Voltage
(4ꢀ μV/°C × 6ꢀ°C) × 1ꢀ6/1ꢀ V
Total Drift Error
RESOLUTION
Noise, Typical, ꢀ.ꢀ1 Hz to 1ꢀ Hz, μV p-p
CMR, 6ꢀ Hz
Nonlinearity
15 μV/1ꢀ V × 1ꢀ6
25 μV/1ꢀ V × 1ꢀ6
2
3
(141 × 1ꢀ-6 × 1 V)/1ꢀ V × 1ꢀ6
(1ꢀ-5 × 1ꢀ V)/1ꢀ V × 1ꢀ6
(141 × 1ꢀ-6 × 2ꢀꢀ V)/1ꢀ V × 1ꢀ6
(5ꢀꢀ × 1ꢀ-6 × 1 V)/1ꢀ V × 1ꢀ6
(1ꢀ-5 × 1ꢀ V)/1ꢀ V × 1ꢀ6
(5ꢀꢀ × 1ꢀ-6 × 2ꢀꢀ V)/1ꢀ V × 1ꢀ6
Total Resolution Error
Total Error
14
5ꢀ
1ꢀ
1ꢀ
AC CMR @ 5ꢀꢀ Hz
282ꢀ
2846
4166
1ꢀ,ꢀꢀꢀ
1ꢀ,ꢀ63
11,6ꢀ3
Rev. C | Page 14 of 16
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