a3242lua Allegro MicroSystems, Inc., a3242lua Datasheet - Page 8

• Manufacturer Part Number: a3242lua
• Description: A3241 And A3242 Chopper-stabilized Unipolar Hall-effect Switches
• Manufacturer: Allegro MicroSystems, Inc.

A3241
A3242
Operation
The output of these devices switches low (turns on) when a
magnetic fi eld (south polarity) perpendicular to the Hall sen-
sor exceeds the operate point threshold, B
output voltage is V
sinking current up to the short circuit current limit, I
is a minimum of 30 mA. When the magnetic fi eld is reduced
below the release point, B
off). The difference in the magnetic operate and release points is
the hysteresis, B
clean switching of the output even in the presence of external
mechanical vibration and electrical noise.
Powering-on the device in the hysteresis region, less than B
and higher than B
correct state is attained after the fi rst excursion beyond B
B
Figure 1: Switching Behavior of Unipolar Switches. In Panel A, on the horizontal axis, the B+ direction indicates increasing south polarity
magnetic fi eld strength, and the B– direction indicates decreasing south polarity fi eld strength (including the case of increasing north
polarity). This behavior can be exhibited when using a circuit such as that shown in panel B.
RP
.
and
hys
V+
RP
0
OUT(SAT)
, of the device. This built-in hysteresis allows
, allows an indeterminate output state. The
B–
RP
0
. The output transistor is capable of
, the device output goes high (turns
(A)
B
HYS
Chopper-Stabilized Unipolar Hall Effect Switches
OP
. After turn-on, the
B+
Functional Description
V
V
OM
CC
OUT(SAT)
, which
OP
OP
or
Applications
It is strongly recommended that an external bypass capacitor be
connected (in close proximity to the Hall sensor) between the
supply and ground of the device to reduce both external noise
and noise generated by the chopper stabilization technique. As is
shown in Panel B of fi gure 1, a 0.1μF capacitor is typical.
Extensive applications information on magnets and Hall-effect
sensors is available in:
• Hall-Effect IC Applications Guide, AN27701,
• Hall-Effect Devices: Gluing, Potting, Encapsulating, Lead
• Soldering Methods for Allegro’s Products – SMT and Through-
All are provided in Allegro Electronic Data Book, AMS-702 and
the Allegro Web site: www.allegromicro.com
Welding and Lead Forming, AN27703.1
Hole, AN26009
V
S
C
0.1 µF
BYP
A324x
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
(B)
VCC
GND
VOUT
R
LOAD
Sensor Output
8