Fully Integrated, Hall Effect-Based Linear Current Sensor IC

with 3 kVRMS Voltage Isolation and a Low-Resistance Current Conductor

ACS756xCB

7

Allegro MicroSystems, LLC

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 mag-

netic circuit sensitivity (G/A) and the linear IC amplifier gain

(mV/G). The linear IC amplifier gain is programmed at the factory

to optimize the sensitivity (mV/A) for the half-scale current of the

device.

The noise floor is derived from the thermal and shot noise

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

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

to resolve.

The degree to which the voltage output from the IC varies in

direct proportion to the primary current through its half-scale

amplitude. Nonlinearity in the output can be attributed to the

saturation of the flux concentrator approaching the half-scale cur-

rent. The following equation is used to derive the linearity:

100 1–

[{

[ {

∆ gain × % sat (

)

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

The degree to which the absolute voltage output from the IC

varies in proportion to either a positive or negative half-scale pri-

mary current. The following equation is used to derive symmetry:

100

Ratiometry

The device features a ratiometric output. This means that the qui-

The ratiometric change (%) in the quiescent voltage output is

defined as:

∆

× 100%

and the ratiometric change (%) in sensitivity is defined as:

=

× 100%

∆

The output of the device when the primary current is zero. For

can be attributed to the resolution of the Allegro linear IC quies-

cent voltage trim, magnetic hysteresis, and thermal drift.

The deviation of the device output from its ideal quiescent value

The magnetic offset is due to 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 mate-

rial used as a flux concentrator. The larger magnetic offsets are

observed at the lower operating temperatures.

The maximum deviation of the actual output from its ideal value,

also referred to as accuracy, illustrated graphically in the output

voltage versus current chart on the following page.

• 0 A at 25°C. Accuracy at the zero current flow at 25°C,

without the effects of temperature.

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

including temperature effects.

• Half-scale current at 25°C. Accuracy at the the half-scale current

at 25°C, without the effects of temperature.

• Half-scale current over Δ temperature. Accuracy at the half-scale

current flow including temperature effects.

DEFINITIONS OF ACCURACY CHARACTERISTICS