ACS70331 datasheet(21/26 Pages) ALLEGRO

21 / 26 page

High Sensitivity, 1 MHz, GMR-Based Current Sensor IC

in Space-Saving, Low Resistance QFN and SOIC-8 Packages

ACS70331

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

Hysteresis (IH). The change in the sensor IC zero current output

voltage after being subjected to a large current for a short dura-

tion. Hysteresis is due to slight magnetization of some of the

ferromagnetic layers in GMR. Pulses of current in opposite direc-

tions will result in hysteresis in opposite directions. The GMR

stack in the ACS70331 is optimized to have low hysteresis in

comparison with more traditional stacks.

Common Mode Field Sensitivity Error Ratio (CMFRSENS).

The ratio of the shift in sensitivity due to an external stray field

on the sensor relative to the field strength (%/G). This is mea-

sured in the worst case stray field configuration.

Common Mode Field Offset Voltage Ratio (CMFROFF). The

ratio of the shift in the offset voltage due to stray field on the sen-

sor relative to the field strength (mV/G). This is measured in the

worst case stray field configuration.

Power Supply Rejection Ratio (PSRR). The ratio of the shift

in VIOUT due to supply voltage variation, expressed in dB. The

PSRR is a small signal parameter, measured with 100 mV pk-pk

over frequency.

log

PSRR

IOUT

Power Supply Offset Error (VOE(PS)). The large signal PSRR,

expressed in absolute millivolts. The power supply offset error is

the variation of the offset voltage over the full supply range of the

ACS70331.

Power Supply Sensitivity Error (ESENS(PS)). The variation in

sensitivity over the full supply range of the ACS70331.

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:

LIN

1–

V(I

)–V

IOUT

PR(max)

IOUT(Q )

2×V(I) –V

IOUT

PR(max/2)

IOUT(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.

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.

DEFINITIONS OF ACCURACY CHARACTERISTICS

Figure 8: Output Voltage versus Sensed Current

Figure 9: 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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