Low Current Ultrasensitive Two-Wire
Chopper-Stabilized Unipolar Hall Effect Switches
A1147 and
A1148
6
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Functional Description
B
HYS
I
CC(H)
I
CC(L)
B+
B
I+
0
(A) A1147
B
HYS
I
CC(H)
I
CC(L)
B+
I+
B
0
(B) A1148
Operation
The output, I
CC
, of the A1147 device switches low after the
magnetic field at the Hall element exceeds the operate point
threshold, B
OP
. When the magnetic field is reduced to below the
release point threshold, B
RP
, the device output goes high. The
differences between the magnetic operate and release point is
called the hysteresis of the device, B
HYS
. This built-in hysteresis
allows clean switching of the output even in the presence of
external mechanical vibration and electrical noise. The A1148
device switches with opposite polarity for similar B
OP
and B
RP
values, in comparison to the A1147 (see figure 1).
Figure 1. Alternative switching behaviors are available in the A114x device family. 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).