A1308 Datasheet, PDF (6/12 Pages) Allegro MicroSystems – Linear Hall-Effect Sensor ICs with Analog Output Available in a Miniature, Low-Profile Surface-Mount Package

A1308 and
A1309
Linear Hall-Effect Sensor ICs with Analog Output
Available in a Miniature, Low-Profile Surface-Mount Package
CHARACTERISTIC DEFINITIONS
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, t_PO , 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), as shown in Figure 1.
Delay to Clamp. A large magnetic input step may cause the
clamp to overshoot its steady-state value. The Delay to Clamp,
t_CLP , is defined as the time it takes for the output voltage to settle
within 1% of its steady-state value, after initially passing through
its steady-state voltage, as shown in Figure 2.
Quiescent Voltage Output. In the quiescent state (no signifi-
cant magnetic field: B = 0 G), the output, V_OUT(Q), is at a con-
stant ratio to the supply voltage, V_CC, across the entire operating
ranges of V_CC and Operating Ambient Temperature, T_A.
Quiescent Voltage Output Drift Across Temperature
Range. Due to internal component tolerances and thermal
considerations, the Quiescent Voltage Output, V_OUT(Q), may
drift due to temperature changes within the Operating Ambient
Temperature, T_A. For purposes of specification, the Quiescent
Voltage Output Drift Across Temperature Range, ∆V_OUT(Q) (mV),
is defined as:
V
V_CC(typ)
90% V_OUT
V_CC
V_OUT
V_CC(min)
t_PO
t₁
t₂
t₁= time at which power supply reaches
minimum specified operating voltage
t₂=
time at which output voltage settles
within ±10% of its steady-state value
under an applied magnetic field
0
+t
Figure 1: Definition of Power-On Time, t_PO
V_CLPHIGH
Magnetic Input Signal
t_CLP
V_OUT
t₁
t₂
t₁= time at which output voltage initially
reaches steady-state clamp voltage
t₂=
time at which output voltage settles to
within 1% of steady-state clamp voltage
time (µs)
Figure 2: Definition of Delay to Clamp, t_CLP
∆V_OUT(Q) = V_OUT(Q)(TA) –V_{OUT(Q)(25°C)}
(1)
Sensitivity. The amount of the output voltage change is propor-
tional to the magnitude and polarity of the magnetic field applied.
This proportionality is specified as the magnetic sensitivity,
Sens (mV/G), of the device and is defined as:
Sens
=
V_OUT(B+) – V_OUT(B–)
(B+) – (B–)
(2)
where B+ is the magnetic flux density in a positive field (south
polarity) and B– is the magnetic flux density in a negative field
(north polarity).
Sensitivity Temperature Coefficient. The device sensitiv-
ity changes as temperature changes, with respect to its Sensitiv-
ity Temperature Coefficient, TC_SENS. TC_SENS is programmed
at 150°C (L temperature device) or at 125°C (K temperature
device), and calculated relative to the baseline sensitivity pro-
gramming temperature of 25°C. TC_SENS is defined as:
TC_Sens
=
^SensST_e²_n–sT^S₁^ensT1
×

100_

_T2¹_–T1
(%/°C)
(3)
where T1 is the baseline Sens programming temperature of 25°C,
and T2 is the TC_SENS programming temperature of 150°C (L
temperature device) or 125°C (K temperature device).
The ideal value of Sens across the full ambient temperature
range, Sens_IDEAL(TA), is defined as:
Sens_IDEAL(TA) = Sens_T1 × [100 (%) + TC_SENS (T_A –T1)] ₍₄₎
Sensitivity Drift Across Temperature Range. Second-
order sensitivity temperature coefficient effects cause the
magnetic sensitivity, Sens, to drift from its ideal value across the
operating ambient temperature range, T_A. For purposes of specifi-
cation, the Sensitivity Drift Across Temperature Range, ∆Sens_TC,
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