A1321, A1322,
and
A1323
Ratiometric Linear Hall Effect Sensor
for High-Temperature Operation
Characteristic Definitions
Ratiometric.
The A132X family features a ratiometric output.
The quiescent voltage output and sensitivity are proportional to
the supply voltage (ratiometric).
The percent ratiometric change in the quiescent voltage output is
defined as:
ΔV
out(q)(ΔV)
=
V
out(q)(V
CC
)
V
out(q)(5V)
V
CC
5 V
× 100%
Quiescent Voltage Output.
In the quiescent state (no
magnetic
fi
eld), the output equals one half of the supply voltage
over the operating voltage range and the operating temperature
range. Due to internal component tolerances and thermal con-
siderations, there is a tolerance on the quiescent voltage output
both as a function of supply voltage and as a function of ambient
temperature. For purposes of specification, the quiescent voltage
output as a function of temperature is defined in terms of mag-
netic
fl
ux density, B, as:
ΔV
out(q)(ΔΤ)
=
V
out(q)(Τ
Α
)
–
V
out(q)(25ºC)
Sens
(25ºC)
(4)
and the percent ratiometric change in sensitivity is
defined as:
ΔSens
(ΔV)
=
Sens
(V
CC
)
Sens
(5V)
V
CC
5 V
× 100%
(1)
(5)
This calculation yields the device’s equivalent accuracy,
over the operating temperature range, in gauss (G).
Sensitivity.
The presence of a south-pole magnetic
fi
eld per-
pendicular to the package face (the branded surface) increases
the output voltage from its quiescent value toward the supply
voltage rail by an amount proportional to the magnetic
fi
eld
applied. Conversely, the application of a north pole will decrease
the output voltage from its quiescent value. This proportionality
is specified as the sensitivity of the device and is defined as:
Sens =
V
out(–B)
–
V
out(+B)
2B
Linearity and Symmetry.
The on-chip output stage
is designed to provide a linear output with a supply voltage of
5 V. Although application of very high magnetic
fi
elds will not
damage these devices, it will force the output into a non-linear
region. Linearity in percent is measured and defined as:
Lin+ =
V
out(+B)
–
V
out(q)
2(V
out(+B / 2)
– V
out(q)
)
V
out(–B)
–
V
out(q)
2(V
out(–B / 2)
– V
out(q)
)
× 100%
(6)
(2)
Lin– =
The stability of sensitivity as a function of temperature is
defined as:
ΔSens
(ΔΤ)
=
Sens
(Τ
Α
)
– Sens
(25ºC)
Sens
(25ºC)
× 100%
× 100%
(7)
and output symmetry as:
(3)
Sym =
V
out(+B)
–
V
out(q)
V
out(q)
– V
out(–B)
× 100%
(8)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
