A3230 ALLEGRO [Allegro MicroSystems], A3230 Datasheet - Page 7

• Manufacturer Part Number: A3230
• Description: Chopper-Stabilized Hall-Effect Bipolar Switch
• Manufacturer: ALLEGRO [Allegro MicroSystems]

Operation
The output of these devices switches low (turns on) when a
magnetic fi eld perpendicular to the Hall sensor exceeds the
operate point threshold, B
is V
up to the short circuit current limit, I
30 mA. When the magnetic fi eld is reduced below the release
point, B
ence in the magnetic operate and release points is the hysteresis,
B
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 fi gure 1, these switchpoints can lie in
either north or south polarity ranges. The values of the magnetic
parameters for the A3230 are specifi ed 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
fi elds of opposite polarity and equivalent strengths are needed
to switch the output. When the magnetic fi elds are removed
(B → 0) the device remains in the same state until a magnetic
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 B
B
such as the A3230, can operate in any of the three modes.
A3230-DS
HYS
HYS
V+
0
OUT(SAT)
band is more positive than B = 0), and panel C shows negative switch behavior (the B
, of the device. This built-in hysteresis allows clean switch-
B–
RP
, the device output goes high (turns off). The differ-
. The output transistor is capable of sinking current
B
HYS
0
(A)
OP
. After turn-on, the output voltage
B+
V
V
CC
OUT(SAT)
Chopper-Stabilized Hall Effect Bipolar Switch
OM
, which is a minimum of
V+
0
Functional Description
B– 0
A3230
B
HYS
(B)
HYS
band incorporates B= 0), panel B shows unipolar switch behavior (the
fi eld of the opposite polarity and of suffi cient strength causes
it to switch. The hysteresis of latch mode behavior is shown in
panel A of fi gure 1.
In contrast to latching, when a device exhibits unipolar switch-
ing, it only responds to a south magnetic fi eld. The fi eld must
be of suffi cient strength, > B
the fi eld is reduced beyond the B
back to the high state, as shown in panel B of fi gure 1. Devices
V
S
B+
V
V
CC
OUT(SAT)
HYS
C
0.1 µF
band is more negative than B = 0). Bipolar devices,
BYP
A3230
V+
0
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
VCC
GND
B–
OP
(D)
, for the device to operate. When
RP
VOUT
level, the device switches
(C)
B
HYS
R
LOAD
0
Sensor Output
B+
V
V
CC
OUT(SAT)
7