A3230ELHLT-T 查看數據表（PDF） - Allegro MicroSystems
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A3230ELHLT-T Datasheet PDF : 12 Pages
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Functional Description
Operation
The output of these devices switches low (turns on) when a
magnetic field perpendicular to the Hall sensor exceeds the
operate point threshold, BOP. After turn-on, the output voltage
is VOUT(SAT). The output transistor is capable of sinking current
up to the short circuit current limit, IOM, which is a minimum of
30 mA. When the magnetic field is reduced below the release
point, BRP, the device output goes high (turns off). The differ-
ence in the magnetic operate and release points is the hysteresis,
BHYS, of the device. This built-in hysteresis allows clean switch-
ing of the output even in the presence of external mechanical
vibration and electrical noise.
There are three switching modes for bipolar devices, referred to
as latch, unipolar switch, and negative switch. Mode is deter-
mined by the switchpoint characteristics of the individual device.
Note that, as shown in figure 1, these switchpoints can lie in
either north or south polarity ranges. The values of the magnetic
parameters for the A3230 are specified in the Magnetic Charac-
teristics table, on page 3.
Bipolar devices typically behave as latches (although these
devices are not guaranteed to do so). In this mode, magnetic
fields of opposite polarity and equivalent strengths are needed
to switch the output. When the magnetic fields are removed
(B → 0) the device remains in the same state until a magnetic
field of the opposite polarity and of sufficient strength causes
it to switch. The hysteresis of latch mode behavior is shown in
panel A of figure 1.
In contrast to latching, when a device exhibits unipolar switch-
ing, it only responds to a south magnetic field. The field must
be of sufficient strength, > BOP, for the device to operate. When
the field is reduced beyond the BRP level, the device switches
back to the high state, as shown in panel B of figure 1. Devices
VS
VCC
CBYP
0.1 µF
A3230
VOUT
GND
RLOAD
Sensor Output
(D)
(A)
(B)
(C)
V+
V+
V+
VCC
VCC
VCC
0
B–
0
VOUT(SAT)
B+
0
B– 0
VOUT(SAT)
B+
0
B–
VOUT(SAT)
0 B+
BHYS
BHYS
BHYS
Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as that shown in panel D. Panel A
displays the hysteresis when a device exhibits latch mode (note that the BHYS band incorporates B= 0), panel B shows unipolar switch behavior (the
BHYS band is more positive than B = 0), and panel C shows negative switch behavior (the BHYS band is more negative than B = 0). Bipolar devices,
such as the A3230, can operate in any of the three modes.
Allegro MicroSystems, Inc.
7
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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