ACS780XLR datasheet(15/24 Pages) ALLEGRO | Core-less, micro-sized, 100 A continuous current package

15 / 24 page

High-Precision Linear Hall-Effect-Based

Current Sensor IC With 200 µΩ Current Conductor

ACS780xLR

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Definitions of Accuracy Characteristics

CHARACTERISTIC DEFINITIONS

SENSITIVITY (Sens)

The change in device output in response to a 1 A change through

the primary conductor. The sensitivity is the product of the mag-

neticcircuitsensitivity(G/A)andthelinearICamplifiergain

(mV/G).ThelinearICamplifiergainisprogrammedatthefactory

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 sensi-

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

to resolve.

NONLINEARITY (ELIN)

The ACS770 is designed to provide a linear output in response

toarampingcurrent.Considertwocurrentlevels:I1andI2.Ide-

ally, the sensitivity of a device is the same for both currents, for

a given supply voltage and temperature. Nonlinearity is present

when there is a difference between the sensitivities measured at

I1 and I2. Nonlinearity is calculated separately for the positive

(ELINpos)andnegative(ELINneg)appliedcurrentsasfollows:

ELINpos = 100 (%) × {1 – (SensIPOS2/ SensIPOS1) }

ELINneg = 100 (%) × {1 – (SensINEG2/ SensINEG1)}

where:

SensIx = (VIOUT(Ix) – VIOUT(Q))/ Ix

and IPOSx and INEGx are positive and negative currents.

Then:

ELIN=max(ELINpos,ELINneg )

RATIOMETRY

The device features a ratiometric output. This means that the

quiescent voltage output, VOUTQ, and the magnetic sensitivity,

Sens, are proportional to the supply voltage, VCC.The ratiometric

change(%)inthequiescentvoltageoutputisdefinedas:

VCC 5 V

VOUT(Q)(VCC) VOUT(Q)(5V)

RatERRVOUT(Q) =

× 100

1 –

( )

andtheratiometricchange(%)insensitivityisdefinedas:

VCC 5 V

Sens(VCC) Sens(5V)

RatERRSens =

× 100

1 –

( )

QUIESCENT OUTPUT VOLTAGE (VOUT(Q))

Theoutputofthedevicewhentheprimarycurrentiszero.For

bidirectional sensors, it nominally remains at VCC⁄2andforuni-

directional sensors at 0.1 × VCC. Thus, VCC = 5 V translates into

VOUT(BI) = 2.5 V and VOUT(QU) = 0.5 V. Variation in VOUT(Q)can

be attributed to the resolution of the Allegro linear IC quiescent

voltage trim and thermal drift.

ELECTRICAL OFFSET VOLTAGE (VOE)

The deviation of the device output from its ideal quiescent value

due to nonmagnetic causes.

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.

ETOTisdividedintofourareas:

• 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.

• Full-scale current at 25°C. Accuracy at 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.

× 100 (%)

ETOT(IP)

VIOUT(IP) – VIOUT_IDEAL(IP)

SensIDEAL × IP

where

VIOUT_IDEAL(IP) = VIOUT(Q)+ (SensIDEAL × IP )

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