ACS722KMATR-20AB-T 查看數據表（PDF） - Allegro MicroSystems

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ACS722KMATR-20AB-T

High Accuracy, Hall-effect Based Current Sensor IC in High Isolation SOIC16 Package

Allegro MicroSystems 

ACS722KMA

High Accuracy, Hall-effect Based Current Sensor

IC in High Isolation SOIC16 Package

APPLICATION INFORMATION

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

CF

where B is the strength of the external field perpendicular to the

surface of the package in Gauss, and CF 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

0.22 A of error. If the ACS722KMATR-10AB, which has a nomi-

nal sensitivity of 132 mV/A, is being used, that equates to 29 mV

of error on the output of the sensor.

Table 1: External Magnetic Field (Gauss) Impact

External Field

(Gauss)

Error (A)

10AB

Error (mV)

20AB

40AB

0.5

0.11

15

7

4

1

0.22

29

15

7

2

0.44

58

29

15

Estimating Total Error vs. Sensed Current

The Performance Characteristics tables give distribution (±3

sigma) values for Total Error at I_PR(max); however, one often

wants to know what error to expect at a particular current. This

can be estimated by using the distribution data for the compo-

nents of Total Error, Sensitivity Error and Offset Voltage. The

±3 sigma value for Total Error (ETOT) as a function of the sensed

current (IP) is estimated as:

( ) ETOT(IP) =

E + 2

SENS

100 × VOE 2

Sens × IP

Here, ESENS and VOE are the ±3 sigma values for those error

terms. If there is an average sensitivity error or average offset

voltage, then the average Total Error is estimated as:

E (I ) = E + TOTAVG P

SENSAVG

100 × VOEAVG

Sens × IP

The resulting total error will be a sum of ETOT and ETOT_AVG.

Using these equations and the 3 sigma distributions for Sensitiv-

ity Error and Offset Voltage, the Total Error vs. sensed current

(IP) is below for the ACS722KMATR-40AB. As expected, as one

goes towards zero current, the error in percent goes towards infin-

ity due to division by zero (refer to Figure 3)

15.00

10.00

5.00

0.00

-5.00

-10.00

-40C+3sig

-40C-3sig

25C+3sig

25C-3sig

125C+3sig

125C-3sig

-15.00

0

5

10

15

20

25

30

35

40

Current (A)

Figure 3: Predicted Total Error as a Function of Sensed

Current for the ACS722KMATR-40AB

Allegro MicroSystems, LLC

13

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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