Information

High Accuracy, Galvanically Isolated Current Sensor IC
With Small Footprint SOIC8 Package
ACS722
19
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Impact of External Magnetic Fields
The ACS722 works by sensing the magnetic field created by the
current flowing through the package. However, the sensor cannot
differentiate between fields created by the current flow and exter-
nal magnetic fields. This means that external magnetic fields can
cause errors in the output of the sensor. Magnetic fields which are
perpendicular to the surface of the package affect the output of
the sensor, as it only senses fields in that one plane. The error in
Amperes can be quantified as:
Error(B) =
B
C
F
where B is the strength of the external field perpendicular to the
surface of the package in Gauss, and C
F
is the coupling factor in
G/A. Then, multiplying by the sensitivity of the part, Sens, gives
the error in mV.
For example, an external field of 1 Gauss will result in around
0.1 A of error. If the ACS722LLCTR-10AB, which has a nominal
sensitivity of 132 mV/A, is being used, that equates to 13.2 mV
of error on the output of the sensor.
External Field
(Gauss)
Error (A)
Error (mV)
5AB 10AB 20AB 40AB
0.5 0.05 13.2 6.6 3.3 1.65
1 0.1 26.4 13.2 6.6 3.3
2 0.2 52.8 26.4 13.2 6.6
APPLICATION INFORMATION