ACS756 View Datasheet(PDF) - Allegro MicroSystems

Part Name

Description

Manufacturer

ACS756

Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 3 kVRMS Voltage Isolation and a Low-Resistance Current Conductor

Allegro MicroSystems 

ACS756

Fully Integrated, Hall Effect-Based Linear Current Sensor IC

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

Definitions of Accuracy Characteristics

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

half-scale current of the device.

Noise (VNOISE). 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.

Nonlinearity (ELIN). 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 current. The following equation is used to derive

the linearity:

{ [ 100 1– Δ gain × % sat ( VIOUT_half-scale amperes –VIOUT(Q))

2 (VIOUT_quarter-scale amperes – VIOUT(Q) )

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

approaches half-scale ±IP , and

VIOUT_half-scale amperes = the output voltage (V) when the

sampled current approximates half-scale ±IP .

Symmetry (ESYM). The degree to which the absolute voltage

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

negative half-scale primary current. The following equation is

used to derive symmetry:

VIOUT_+ half-scale amperes –VIOUT(Q)

  100 VIOUT(Q) – VIOUT_–half-scale amperes

Ratiometry. The device features a ratiometric output. This

means that the quiescent voltage output, VIOUTQ, and the mag-

netic sensitivity, Sens, are proportional to the supply voltage, VCC.

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

defined as:

$VIOUTQ($V) =

VIOUTQ(VCC) VIOUTQ(5V)

s%

VCC 5 V

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

$Sens($V = Sens(VCC

Sens(V

VCC 5 V

s%

Quiescent output voltage (VIOUT(Q)). The output of the device

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

it nominally remains at VCC ⁄ 2. Thus, VCC = 5 V translates into

VIOUT(Q) = 2.5 V. Variation in VOUT(Q) can be attributed to the res-

olution of the Allegro linear IC quiescent voltage trim, magnetic

hysteresis, and thermal drift.

Electrical offset voltage (VOE). The deviation of the device out-

put from its ideal quiescent value of VCC ⁄ 2 due to nonmagnetic

causes.

Magnetic offset error (IERROM). 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 material used as a flux concentrator.

The larger magnetic offsets are observed at the lower operating

temperatures.

Total Output Error (ETOT). 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.

ETOT 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.

 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.

Allegro MicroSystems, Inc.

7

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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