3185
THRU
3189
HALL-EFFECT LATCHES
FOR HIGH-TEMPERATURE
OPERATION
SENSOR LOCATIONS
(±0.005” [0.13 mm] die placement)
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.
Package Designators “LT”
ACTIVE AREA DEPTH
0.030"
0.76 mm
NOM
0.090"
2.27 mm
0.050"
1.27 mm
A
1
2
3
Dwg. MH-008-4B
Package Designator “U”
ACTIVE AREA DEPTH
0.015"
0.38 mm
NOM
0.092"
2.33 mm
30 V
MAX
V
BB
0.077"
1.96 mm
OUTPUT VOLTAGE IN VOLTS
B
RP
B
OP
A
BRANDED
SURFACE
1
2
3
V
OUT(SAT)
0
-B
0
FLUX DENSITY
Dwg. MH-002-7B
+B
Dwg. GH-034-4
Package Designators “UA” and "UA-TL"
ACTIVE AREA DEPTH
0.018"
0.46 mm
NOM
0.083"
2.10 mm
The simplest form of magnet that will operate these devices is a ring
magnet, as shown below. Other methods of operation are possible.
0.060"
1.51 mm
A
BRANDED
SURFACE
1
2
3
Dwg. A-11,899
Dwg. MH-011-4B
Although sensor location is accurate to three
sigma for a particular design, product improve-
ments may result in small changes to sensor
location.
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.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
