ACS730 datasheet(13/18 Pages) ALLEGRO

13 / 18 page

1 MHz Bandwidth, Galvanically Isolated Current Sensor IC

in Small Footprint SOIC8 Package

ACS730

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 sensor IC output in response to

a 1A 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 ampli-

fier 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 sensor IC is over the full current measurement

range. The nonlinearity is calculated as:

ELIN =

VIOUT (IR(max)) – VIOUT(Q)

2 • VIOUT (IR(max)/2) – VIOUT(Q)

• 100(%)

{

}

1 –

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 2.5 V for a bidirectional device.

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 2.5 V due to nonmagnetic causes. To

convert this voltage to amperes, divide by the device sensitivity,

Sens.

Total Output Error (ETOT). The difference between the cur-

rent 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

• 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 Figure

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

versus IP at 25°C and across temperature. Figure 2 shows the cor-

responding ETOT versus IP.

DEFINITIONS OF ACCURACY CHARACTERISTICS

Figure 1: Output Voltage versus Sensed Current

Figure 2: Total Output Error versus Sensed Current

0 A

Decreasing

VIOUT (V)

Accuracy Across

Temperature

Accuracy Across

Temperature

Accuracy Across

Temperature

Accuracy at

25°C Only

Accuracy at

25°C Only

Accuracy at

25°C Only

Increasing

VIOUT (V)

Ideal VIOUT

IPR(min)

IPR(max)

+IP (A)

–IP (A)

VIOUT(Q)

Full Scale IP

+IP

–IP

+ETOT

–ETOT

Across Temperature

25°C Only

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