AD629

Rev. B | Page 13 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 39). 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 (+)

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

10 AMPS

±100V AC CM

TO GROUND

Error, ppm of FS

Error Source

AD629

INA117

AD629

INA117

Initial Gain Error

500

500

Offset Voltage

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

120

240

Total Drift Error

720

840

RESOLUTION

Noise, Typical, 0.01 Hz to 10 Hz, μV p-p

2

3

CMR, 60 Hz

14

50

Nonlinearity

10

10

AC CMR @ 500 Hz

2820

10,000

Total Resolution Error

2846

10,063

Total Error

4166

11,603