Data Sheet
27621.30A‡
3161
HALL-EFFECT SWITCH
FOR 2-WIRE APPLICATIONS
This Hall-effect switch is a monolithic integrated circuit designed to
operate continuously over extended temperatures to +85°C. The unipo-
lar switching characteristic makes this device ideal for use with a simple
bar or rod magnet. The A3161ELT and A3161EUA are identical except
for package.
Each device includes a voltage regulator for operation with supply
voltages of 3.5 to 25 volts, reverse battery protection diode, quadratic
Hall-voltage generator, temperature compensation circuitry, small-signal
amplifier, Schmitt trigger, and a constant-current open-collector output.
Noise radiation is limited by control of the output current slew rate.
Two package styles provide a magnetically optimized package for
most applications. Suffix ‘LT’ is a miniature SOT-89/TO-243AA
transistor package for surface-mount applications; suffix ‘UA’ is a three-
lead ultra-mini SIP for through-hole mounting.
V
X
CC
1
2
3
GROUND
Dwg. PH-003-3
OUTPUT
SUPPLY
FEATURES and BENEFITS
I
I
I
I
I
I
I
I
I
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25
°
C
Supply Voltage, V
CC
Continuous .................................
28 V
Surge (t
w
≤
100 ms) ....................
40 V
Reverse Battery Voltage, V
RCC
Continuous ................................
-25 V
Surge (t
w
≤
100 ms) ...................
-40 V
Magnetic Flux Density, B .......
Unlimited
Output OFF Voltage, V
OUT
..............
28 V
Operating Temperature Range,
T
A
.............................
-40
°
C to +85
°
C
Storage Temperature Range,
T
S
...........................
-65
°
C to +170
°
C
Internal Current Regulator for 2-Wire Operation
Output Slew Rate Controlled
3.5 V to 25 V Operation … Needs Only An Unregulated Supply
Reverse Battery Protection
Excellent Temp. Stability
Activate with Small, Commercially Available Permanent Magnets
Small Size
Solid-State Reliability … No Moving Parts
Resistant to Physical Stress
Always order by complete part number, e.g.,
A3161ELT .
3161
HALL-EFFECT SWITCH
FOR 2-WIRE APPLICATIONS
ELECTRICAL CHARACTERISTICS over operating voltage and temperature ranges.
Limits
Characteristic
Supply Voltage
Load Current
(2-wire application)
Symbol
V
CC
I
OUT
+ I
CC
Test Conditions
Operating
3.5 V
≤
V
OUT
< 12 V, B < B
RP
V
OUT
≥
12 V, B < B
RP
B > B
OP
Output Current
I
OUT
I
OFF
Output Saturation Voltage
Output Slew Rate
Output Settling Time
V
OUT
di/dt
t
sd
B < B
RP
V
OUT
= 24 V, B > B
OP
I
OUT
= 5 mA, B < B
RP
C
L
= 20 pF
C
L
= 20 pF
Min.
3.5
12
12
—
—
—
–
—
—
Typ.
—
15
15
3.5
12
<1.0
0.9
7.0
—
Max.
25
17
19
5.0
—
10
1.5
20
20
Units
V
mA
mA
mA
mA
µA
V
mA/µs
µs
MAGNETIC CHARACTERISTICS over operating supply voltage range.
Limits
At T
A
= +25
°
C
Characteristic
Operate Point (output turns OFF)
Release Point (output turns ON)
Hysteresis (B
OP
- B
RP
)
Symbol
B
OP
B
RP
B
hys
Min.
–
30
5.0
Typ.
130
110
20
Max.
160
–
–
Over Oper. Temp. Range
Min.
–
30
5.0
Typ.
130
110
20
Max.
160
–
80
Units
G
G
G
NOTE:Typical values are at T
A
= +25°C and V
CC
= 12 V.
FUNCTIONAL BLOCK DIAGRAM
1
V
CC
3
OUTPUT
REG.
X
2
GROUND
Dwg. FH-017
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1998, 1999, Allegro MicroSystems, Inc.
3161
HALL-EFFECT SWITCH
FOR 2-WIRE APPLICATIONS
SENSOR LOCATIONS
Suffix “LT”
ACTIVE AREA DEPTH
0.030"
0.76 mm
NOM
0.085"
2.16 mm
0.045"
1.14 mm
OPERATION
The output of these devices (pin 3) switches OFF when the magnetic
field at the Hall sensor exceeds the operate point threshold (B
OP
). When the
magnetic field is reduced to below the release point threshold (B
RP
), the
device output switches ON. The difference in the magnetic operate and
release points is called the hysteresis (B
hys
) of the device. This built-in
hysteresis allows clean switching of the output even in the presence of
external mechanical vibration and electrical noise.
15
A
1
2
3
12
B
OP
Dwg. MH-008-7
OUTPUT CURRENT in mA
9.0
Suffix “UA”
ACTIVE AREA DEPTH
0.018"
0.46 mm
NOM
0.078"
1.98 mm
6.0
T
A
= +25°C
3.0
B
RP
A
BRANDED
SURFACE
1
2
3
0.054"
1.36 mm
0
0
25
50
75
100
125
150
175
200
MAGNETIC FLUX DENSITY in GAUSS
Dwg. GH-007-1
APPLICATIONS INFORMATION
Dwg. MH-011-8
Allegro
These devices are normally operated in a 2-wire mode, where the supply
terminal and the output terminal are tied together. An external comparator
detects the change in total supply current by the addition (output off, B > B
OP
)
or subtraction (output on, B < B
RP
) of I
OUT
.
Hall effect applications information is available in the “Hall-Effect IC
Applications Guide”, which can be found in the latest issue of the
Allegro
MicroSystems Electronic Data Book,
AMS-702 or
Application Note
27701,
or at
www.allegromicro.com
.
TYPICAL 2-WIRE APPLICATION
SUPPLY
Icc + Io
UT
3
0.1
µF
0.85 V
–
+
2
X
V
CC
100
Ω
Dwg. EH-011A
1
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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