Ultrasensitive Two-Wire Field-Programmable
Chopper-Stabilized Unipolar Hall Effect Switches
A1185 and
A1186
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) A1185
B
HYS
I
CC(H)
I
CC(L)
B+
I+
B
0
(B) A1186
The output, I
CC
, of the A1185 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 differ-
ences 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 A1186 device
switches with opposite polarity for similar B
OP
and B
RP
values,
in comparison to the A1185 (see figure 1).
Figure 1. Alternative switching behaviors are available in the A118x 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).
Operation