Datasheet

Linear Hall Effect Sensor ICs with Analog Output
A1324, A1325,
and A1326
5
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Power-On Time When the supply is ramped to its operating
voltage, the device output requires a finite time to react to an
input magnetic field. Power-On Time is defined as the time it
takes for the output voltage to begin responding to an applied
magnetic field after the power supply has reached its minimum
specified operating voltage, V
CC
(min).
V
+t
V
CC
V
CC
(min.)
V
OUT
90% V
OUT
0
t
1
= time at which power supply reaches
minimum specified operating voltage
t
2
= time at which output voltage settles
within ±10% of its steady state value
under an applied magnetic field
t
1
t
2
t
PO
V
CC
(typ.)
Quiescent Voltage Output In the quiescent state (that is, with
no significant magnetic field: B = 0), the output, V
OUT(Q)
, equals
a ratio of the supply voltage, V
CC
, throughout the entire operat-
ing range of V
CC
and the ambient temperature, T
A
.
Quiescent Voltage Output Drift Through Temperature
Range Due to internal component tolerances and thermal con-
siderations, the quiescent voltage output, V
OUT(Q)
, may drift from
its nominal value through the operating ambient temperature
range, T
A
. For purposes of specification, the Quiescent Voltage
Output Drift Through Temperature Range, ∆V
OUT(Q)
(mV), is
defined as:
∆V
OUT(Q)
V
OUT(Q)TA
– V
OUT(Q)25°C
=
(1)
Sensitivity The presence of a south-polarity magnetic field
perpendicular to the branded surface of the package increases the
output voltage from its quiescent value toward the supply voltage
rail. The amount of the output voltage increase is proportional
to the magnitude of the magnetic field applied. Conversely, the
application of a north polarity field will decrease the output volt-
age from its quiescent value. This proportionality is specified
as the magnetic sensitivity, Sens (mV/G), of the device and is
defined as:
V
OUT(B+)
– V
OUT(B–)
B(+) – B(–)
Sens
=
(2)
where B(+) and B(–) are two magnetic fields with opposite
polarities.
Sensitivity Temperature Coefficient The device sensitivity
changes with temperature, with respect to its sensitivity tem-
perature coefficient, TC
SENS
. TC
SENS
is programmed at 150°C,
and calculated relative to the nominal sensitivity programming
temperature of 25°C. TC
SENS
(%/°C) is defined as:
Sens
T2
– Sens
T1
Sens
T1
T2–T1
1
TC
Sens
=
×
100%
















(3)
where T1 is the nominal Sens programming temperature of 25°C,
and T2 is the TC
SENS
programming temperature of 150°C.
The ideal value of sensitivity through the temperature range,
Sens
IDEAL(TA)
, is defined as:
Sens
T1
× (100% + TC
SENS(TA –T1)
)
S
ens
IDEAL(TA)
=
(4)
Sensitivity Drift Through Temperature Range Second
order sensitivity temperature coefficient effects cause the mag-
netic sensitivity to drift from its ideal value through the operating
ambient temperature, T
A
. For purposes of specification, the sensi-
tivity drift through temperature range, ∆Sens
TC
, is defined as:
Sens
TA
– Sens
IDEAL(TA)
Sens
IDEAL(TA)
∆Sens
TC
=
×
100%
(5)
Sensitivity Drift Due to Package Hysteresis Package
stress and relaxation can cause the device sensitivity at T
A
= 25°C
to change during or after temperature cycling. This change in
sensitivity follows a hysteresis curve.
For purposes of specification, the Sensitivity Drift Due to Pack-
age Hysteresis, ∆Sens
PKG
, is defined as:
Sens
(25°C)2
– Sens
(25°C)1
Sens
(25°C)1
∆Sens
PKG
=
×
100%
(6)
where Sens
(25°C)1
is the programmed value of sensitivity at
Characteristic Definitions