ACS712 データシートの表示（PDF） - Allegro MicroSystems

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ACS712

Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor

Allegro MicroSystems 

ACS712

Fully Integrated, Hall Effect-Based Linear Current Sensor IC

with 2.1 kVRMS 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

full-scale current of the device.

Noise (VNOISE). The product of the linear IC amplifier gain

(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.

Linearity (ELIN). The degree to which the voltage output from

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:

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

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

where VIOUT_full-scale amperes = the output voltage (V) when the

sampled current approximates full-scale ±IP .

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

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

negative full-scale primary current. The following formula is

used to derive symmetry:

VIOUT_+ full-scale amperes – VIOUT(Q)

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

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 VIOUT(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 out-

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

causes. To convert this voltage to amperes, divide by the device

sensitivity, Sens.

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.

Ratiometry. The ratiometric feature means that its 0 A output,

VIOUT(Q), (nominally equal to VCC/2) and sensitivity, Sens, are

proportional to its supply voltage, VCC . The following formula is

used to derive the ratiometric change in 0 A output voltage,

VIOUT(Q)RAT (%).

VIOUT(Q)VCC / VIOUT(Q)5V

100 

VCC / 5 V



The ratiometric change in sensitivity, SensRAT (%), is defined as:

SensVCC / Sens5V

100

‰  VCC / 5 V

–IP (A)

Output Voltage versus Sampled Current

Accuracy at 0 A and at Full-Scale Current

Increasing VIOUT(V)

Accuracy

Over $Temp erature

Accuracy

25°C Only

Accuracy

Over $Temp erature

Average

VIOUT

IP(min)

Accuracy

25°C Only

0A

Full Scale

IP(max)

+IP (A)

Accuracy (ETOT). The accuracy represents the maximum devia-

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 at right.

Accuracy

25°C Only

Accuracy

Over $Temp erature

Decreasing VIOUT(V)

Allegro MicroSystems, Inc.

9

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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