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3185
THRU
3189
HALL-EFFECT LATCHES
FOR HIGH-TEMPERATURE
OPERATION
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
SENSOR LOCATIONS
(
±
0.005” [0.13 mm] die placement)
Allegro
Package Designators “LT”
1
3
2
Dwg. MH-008-4C
0.0305"
0.775 mm
NOM
ACTIVE AREA DEPTH
0.050"
1.27 mm
0.090"
2.27 mm
A
Package Designators “UA”
1
3
2
Dwg. MH-011-4C
0.0195"
0.50 mm
NOM
BRANDED
SURFACE
ACTIVE AREA DEPTH
0.083"
2.10 mm
0.060"
1.51 mm
A
The simplest form of magnet that will operate these devices is a ring
magnet, as shown below. Other methods of operation are possible.
Dwg. A-11,899
OPERATION
In operation, the output transistor is OFF until the strength of the mag-
netic field perpendicular to the surface of the chip exceeds the threshold or
operate point (B
OP
). When the field strength exceeds B
OP
, the output transis-
tor switches ON and is capable of sinking 25 mA of current.
The output transistor switches OFF when magnetic field reversal results
in a magnetic flux density below the OFF threshold (B
RP
). This is illustrated
in the transfer characteristics graph (A3187* shown).
Note that the device latches; that is, a south pole of sufficient strength
will turn the device ON. Removal of the south pole will leave the device ON.
The presence of a north pole of sufficient strength is required to turn the
device OFF. Powering up in the absence of a magnetic field (less than B
OP
and higher than B
RP
) will allow an indeterminate output state. The correct
state is warranted after the first excursion beyond B
OP
or B
RP
.
APPLICATIONS INFORMATION
Extensive applications information on magnets and Hall-effect sensors is
also available in the
Allegro Integrated and Discrete Semiconductors Data
Book
or
Application Note
27701.
30 V
MAX
0
+B
0
O
FLUX DENSITY
Dwg. GH-034-4
-B
RP
B
V
OUT(SAT)
BB
V
OP
B
Although sensor location is accurate to three
sigma for a particular design, product improve-
ments may result in small changes to sensor
location.