Hall Effect Linear Current Sensor with Overcurrent
Fault Output for < 100 V Isolation Applications
ACS711
Definitions of Accuracy Characteristics
Sensitivity (Sens). The change in sensor 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.
Accuracy (ETOT). The accuracy represents the maximum devia-
tion of the actual output from its ideal value. This is also known
as the total ouput error. The accuracy is illustrated graphically in
the output voltage versus current chart below.
Ratiometry. The ratiometric feature means that its 0 A output,
VIOUT(Q), (nominally equal to VCC/2) and sensitivity, Sens, are
Noise (VNOISE). The product of the linear IC amplifier gain (mV)
and the noise floor for the Allegro Hall effect linear IC. The noise
floor is derived from the thermal and shot noise observed in Hall
elements. Dividing the noise (mV) by the sensitivity (mV/A) pro-
vides the smallest current that the device is able to resolve.
proportional to its supply voltage, VCC.The following formula is
used to derive the ratiometric change in 0 A output voltage,
VIOUT(Q)RAT (%):
V
IOUT(Q)VCC / VIOUT(Q)3.3V
100
Linearity (ELIN). The degree to which the voltage output from
the sensor varies in direct proportion to the primary current
through its full-scale amplitude. Nonlinearity in the output can be
attributed to the saturation of the flux concentrator approaching
the full-scale current. The following equation is used to derive the
linearity:
VCC
/
3.3 V
The ratiometric change in sensitivity, SensRAT (%), is defined as:
SensVCC / Sens3.3V
100
VCC
/
3.3 V
V
– VIOUT(Q)
Δ gain × % sat (
IOUT_full-scale amperes
2 (VIOUT_half-scale amperes – VIOUT(Q)
100
1–
{
[
) [ {
)
Output Voltage versus Sensed Current
Accuracy at 0 A and at Full-Scale Current
where VIOUT_full-scale amperes = the output voltage (V) when the
sensed current approximates full-scale ±IP .
Increasing VIOUT(V)
Accuracy
Over $Temp erature
Symmetry (ESYM). The degree to which the absolute voltage
output from the sensor varies in proportion to either a positive
or negative full-scale primary current. The following formula is
used to derive symmetry:
Accuracy
25°C Only
Average
V
IOUT
Accuracy
Over $Temp erature
VIOUT_+ full-scale amperes – VIOUT(Q)
100
V
IOUT(Q)
– VIOUT
–full-scale amperes
Accuracy
25°C Only
Quiescent output voltage (VIOUT(Q)). The output of the sensor
when the primary current is zero. For a unipolar supply voltage,
it nominally remains at VCC ⁄ 2. Thus, 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.
IP(min)
–IP (A)
+IP (A)
Full Scale
IP(max)
0 A
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
25°C Only
Accuracy
Over $Temp erature
Decreasing VIOUT(V)
Allegro MicroSystems, LLC
115 Northeast Cutoff
13
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
