ACS70331 datasheet(13/26 Pages) ALLEGRO

13 / 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

Gain and Offset Trim

The bridge configuration of the GMR elements in the ACS70331

make the gain and offset trim for the sensor relatively simple. As

the bridge output voltage is proportional to the voltage driving it,

that voltage is trimmed to compensate for all other nominal gain

errors, as well as errors over temperature. Then, offset is trimmed

out after the bridge voltage has been amplified. All trim codes are

stored using fuses that are programmed at final test before lock-

ing the part.

Ideal Output Transfer Curve

The ideal output of the ACS70331 is:

VIOUT = Sens × IP + VIOUT(Q)

Different versions of the ACS70331 have different sensitivity

(Sens) and zero current output voltage (VIOUT(Q)) values in order

to give different current measurement ranges. Unidirectional

sensors start at 0.25 V with zero current through the primary and

swing +2 V for full-scale current. Bidirectional sensors start at

1.5 V with zero current through the primary and swing ±1 V for

full-scale current. Figure 4 shows the ideal output transfer curves

for each version of the ACS70331. The output curves show the

typical saturation levels; however, the saturation could occur

anywhere beyond the min/max saturation limits shown by the

dashed lines. The stated accuracy of the sensor is only valid over

the given current sensing range (IPR).

2.5

1.5

0.5

-6

-4

-2

IP (A)

2.5 Unidirectional

2.5 Bidirectional

5 Unidirectional

5 Bidirectional

Vsat-high

Vsat-low

Figure 4: Ideal Output Tranfer Curves

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