ACS722 查看數據表（PDF） - Allegro MicroSystems

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ACS722

High Accuracy, Galvanically Isolated Current Sensor IC With Small Footprint SOIC8 Package

Allegro MicroSystems 

ACS722

High Accuracy, Galvanically Isolated Current Sensor IC

With Small Footprint SOIC8 Package

DEFINITIONS OF ACCURACY CHARACTERISTICS

Sensitivity (Sens)

The change in sensor IC output in response to a 1 A change

through the primary conductor. The sensitivity is the product of

the magnetic circuit sensitivity (G / A) (1 G = 0.1 mT)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 full-scale current of the device.

Nonlinearity (ELIN)

The nonlinearity is a measure of how linear the output of the sen-

sor IC is over the full current measurement range. The nonlinear-

ity is calculated as:

{ [ ELIN =

1–

VIOUT (IPR(max)) – VIOUT(Q)

2 × VIOUT (IPR(max)/2) – VIOUT(Q)

× 100 (%)

where VIOUT(IPR(max)) is the output of the sensor IC with the

maximum measurement current flowing through it and

VIOUT(IPR(max)/2) is the output of the sensor IC with half of the

maximum measurement current flowing through it.

Zero Current Output Voltage (VIOUT(Q))

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

a unipolar supply voltage, it nominally remains at 0.5 × VCC for

a bidirectional device and 0.1 × VCC for a unidirectional device.

For example, in the case of a bidirectional output device, VCC =

3.3 V translates into VIOUT(Q) = 1.65 V. Variation in VIOUT(Q) can

be attributed to the resolution of the Allegro linear IC quiescent

voltage trim and thermal drift.

Offset Voltage (VOE)

The deviation of the device output from its ideal quiescent value

of 0.5 × VCC (bidirectional) or 0.1 × VCC (unidirectional) due to

nonmagnetic causes. To convert this voltage to amperes, divide

by the device sensitivity, Sens.

Total Output Error (ETOT)

The difference between the current measurement from the sensor

IC and the actual current (IP), relative to the actual current. This

is equivalent to the difference between the ideal output voltage

and the actual output voltage, divided by the ideal sensitivity,

relative to the current flowing through the primary conduction

path:

ETOT(IP) =

VIOUT_ideal(IP) – VIOUT(IP)

Sensideal(IP) × IP

×

100

(%)

The Total Output Error incorporates all sources of error and is a

function of IP . At relatively high currents, ETOT will be mostly

due to sensitivity error, and at relatively low currents, ETOT will

be mostly due to Offset Voltage (VOE ). In fact, at IP = 0, ETOT

approaches infinity due to the offset. This is illustrated in Figures

1 and 2. Figure 1 shows a distribution of output voltages versus IP

at 25°C and across temperature. Figure 2 shows the correspond-

ing ETOT versus IP .

Increasing

VIOUT (V)

Accuracy Across

Temperature

Accuracy at

25°C Only

Accuracy Across

Temperature

Ideal VIOUT

Accuracy at

25°C Only

IPR(min)

–IP (A)

VIOUT(Q)

+IP (A)

Full Scale IP

IPR(max)

0A

Accuracy at

25°C Only

Accuracy Across

Temperature

Decreasing

VIOUT (V)

Figure 1: Output Voltage versus Sensed Current

+ETOT

Across Temperature

25°C Only

–IP

+IP

–ETOT

Figure 2: Total Output Error versus Sensed Current

Allegro MicroSystems, LLC

18

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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