Fully Integrated, Hall Effect-Based Linear Current Sensor IC

with High Voltage Isolation and a Low-Resistance Current Conductor

ACS754xCB-200

5

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Sensitivity (Sens). The change in device output in response to a

1A change through the primary conductor. The sensitivity is the

product of the magnetic circuit sensitivity (G /A) and the linear

IC amplifier gain (mV/G). The linear IC amplifier gain is pro-

grammed at the factory to optimize the sensitivity (mV/A) for the

full-scale current of the device.

(mV/G) and the noise floor for the Allegro Hall effect linear IC

(≈1 G). The noise floor is derived from the thermal and shot

noise observed in Hall elements. Dividing the noise (mV) by the

sensitivity (mV/A) provides the smallest current that the device is

able to resolve.

the IC varies in direct proportion to the primary current through

its full-scale amplitude. Nonlinearity in the output can be attrib-

uted to the saturation of the flux concentrator approaching the

full-scale current. The following equation is used to derive the

linearity:

where

∆ gain = the gain variation as a function of temperature

changes from 25ºC,

% sat = the percentage of saturation of the flux concentra-

tor, which becomes significant as the current being sampled

output from the IC varies in proportion to either a positive or

negative full-scale primary current. The following equation is

used to derive symmetry:

when the primary current is zero. For a unipolar supply voltage,

olution of the Allegro linear IC quiescent voltage trim, magnetic

hysteresis, and thermal drift.

causes.

the residual magnetism (remnant field) of the core material. The

magnetic offset error is highest when the magnetic circuit has

been saturated, usually when the device has been subjected to a

full-scale or high-current overload condition. The magnetic offset

is largely dependent on the material used as a flux concentrator.

The larger magnetic offsets are observed at the lower operating

temperatures.

tion of the actual output from its ideal value. This is also known

as the total output error. The accuracy is illustrated graphically in

the output voltage versus current chart on the following page.

Accuracy is divided into four areas:

 0 A at 25°C. Accuracy at the zero current flow at 25°C, with-

out the effects of temperature.

 0 A over Δ temperature. Accuracy at the zero current flow

including temperature effects.

 Full-scale current at 25°C. Accuracy at the the full-scale current

at 25°C, without the effects of temperature.

 Full-scale current over Δ temperature. Accuracy at the full-

scale current flow including temperature effects.

Definitions of Accuracy Characteristics

100 1–

[

{

[ {

Δ gain × % sat (

)

100

