A3245 データシートの表示（PDF） - Allegro MicroSystems
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A3245 Datasheet PDF : 12 Pages
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A3245
Chopper-Stabilized Omnipolar Hall Effect Switches
Functional Description
Operation
The output of this device switches low (turns on) when a mag-
netic field perpendicular to the Hall sensor exceeds the operate
point, BOPS (or is less than BOPN). After turn-on, the output
voltage is VOUT(SAT). The output transistor is capable of sink-
ing 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, BRPS (or increased above BRPN), the device
output switches high (turns off). The difference in the magnetic
operate and release points is the hysteresis, BHYS , of the device.
This built-in hysteresis allows clean switching of the output even
in the presence of external mechanical vibration and electrical
noise.
Powering-on the device in a hysteresis region, between BOPX
and BRPX, allows an indeterminate output state. The correct state
is attained after the first excursion beyond BOPX or BRPX.
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 figure 1, a 0.1μF capacitor is typical.
Omnipolar switches allow operation with either a north pole or
south pole magnet orientation, enhancing product manufactur-
ability with the device.
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
Welding and Lead Forming, AN27703.1
• Soldering Methods for Allegro’s Products – SMT and Through-
Hole, AN26009
All are provided in Allegro Electronic Data Book, AMS-702 and
the Allegro Web site: www.allegromicro.com
(A)
V+
VS
VS
0
B–
BHYS
0
BHYS
VOUT(SAT)
B+
(B)
VCC
CBYP
0.1 μF
A3245
VOUT
GND
RLOAD
Sensor Output
Figure 1: Switching Behavior of Omnipolar Switches. In Panel A, on the horizontal axis, the B+ direction indicates increasing south polarity
magnetic field strength, and the B– direction indicates decreasing south polarity field strength (including the case of increasing north
polarity). This behavior can be exhibited when using a circuit such as that shown in panel B.
Allegro MicroSystems, Inc.
8
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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