AD629
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, so that this interference
component can be neglected.
OUTPUT
CURRENT
21.1k⍀
REF(–)
–IN
10 AMPS
200V DC
TO GROUND
1
2
3
4
8
7
6
5
NC
CM
380k⍀ 380k⍀
+V
0.1F
S
1⍀
SHUNT
380k⍀
20k⍀
+IN
V
OUTPUT
CURRENT
OUT
REF(+)
REF(–)
–IN
21.1k⍀
60Hz
POWER LINE
10 AMPS
؎100V AC CM
TO GROUND
–V
1
2
3
4
8
7
6
5
NC
S
AD629
0.1F
380k⍀ 380k⍀
NC = NO CONNECT
+V
S
1⍀
SHUNT
0.1F
380k⍀
20k⍀
Figure 37. 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
+IN
V
OUT
REF(+)
60Hz
POWER LINE
–V
S
AD629
0.1F
Error Budget Analysis Example 2
NC = NO CONNECT
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 (Figure 38). All other conditions are the same as
Figure 38. Error Budget Analysis Example 2. VIN = 10 V
Full-Scale, VCM 100 V at 500 Hz, RSHUNT = 1 Ω
=
Table IV. AD629 vs. INA117 AC Error Budget Example 2 (VCM = ؎100 V @ 500 Hz)
Error, ppm of FS
Error Source
AD629
INA117
AD629
INA117
ACCURACY, TA = 25°C
Initial Gain Error
Offset Voltage
(0.0005 × 10) ÷ 10 V × 106
(0.001 V ÷ 10 V) × 106
(0.0005 × 10) ÷ 10 V × 106
(0.002 V ÷ 10 V) × 106
500
100
500
200
Total Accuracy Error:
600
700
TEMPERATURE DRIFT (85°C)
Gain
10 ppm/°C × 60°C
10 ppm/°C × 60°C
600
120
600
240
Offset Voltage
(20 µV/°C × 60°C) × 106/10 V
(40 µV/°C × 60°C) × 106/10 V
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
14
10
3
50
10
CMR @ 60 Hz
Nonlinearity
AC CMR @ 500 Hz
(141 × 10–6 × 1 V) ÷ 10 V × 106
(10–5 × 10 V) ÷ 10 V × 106
(500 × 10–6 × 1 V) ÷ 10 V × 106
(10–5 × 10 V) ÷ 10 V × 106
(141 × 10–6 × 200 V) ÷ 10 V × 106 (500 × 10–6 × 200 V) ÷ 10 V × 106
2,820
10,000
Total Resolution Error: 2,846
Total Error: 4,166
10,063
11,603
REV. A
–11–