3121, 3122,
AND
3123
HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE OPERATION
These Hall-effect switches are monolithic integrated circuits with
tighter magnetic specifications, designed to operate continuously over
extended temperatures to +150°C, and are more stable with both tem-
perature and supply voltage changes. The unipolar switching character-
istic makes these devices ideal for use with a simple bar or rod magnet.
The three basic devices (A3121, A3122, and A3123) are identical except
for magnetic switch points.
Each device includes a voltage regulator for operation with supply
voltages of 4.5 volts to 24 volts, reverse battery protection diode, qua-
dratic Hall-voltage generator, temperature compensation circuitry, small-
signal amplifier, Schmitt trigger, and an open-collector output to sink up
to 25 mA. With suitable output pull up, they can be used with bipolar or
CMOS logic circuits. The A3121 is an improved replacement for the
UGx3113 and UGx3119.
The first character of the part number suffix determines the device
operating temperature range. Suffix ‘E–’ is for the automotive and
industrial temperature range of -40°C to +85°C. Suffix ‘L–’ is for the
automotive and military temperature range of -40°C to +150°C. Two
package styles provide a magnetically optimized package for most
applications. Suffix ‘–LT’ is a miniature SOT89/TO-243AA transistor
package for surface-mount applications; suffix ‘–UA’ is a three-lead
ultra-mini-SIP.
Data Sheet
27621.4C*
V
X
CC
1
2
3
GROUND
Dwg. PH-003A
Pinning is shown viewed from branded side.
OUTPUT
SUPPLY
FEATURES and BENEFITS
s
Superior Temp. Stability for Automotive or Industrial Applications
s
4.5 V to 24 V Operation … Needs Only An Unregulated Supply
s
Open-Collector 25 mA Output … Compatible with Digital Logic
s
Reverse Battery Protection
s
Activate with Small, Commercially Available Permanent Magnets
s
Solid-State Reliability … No Moving Parts
s
Small Size
s
Resistant to Physical Stress
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25
°
C
Supply Voltage, V
CC
...........................
30 V
Reverse Battery Voltage, V
RCC
........
-30 V
Magnetic Flux Density, B .......
Unlimited
Output OFF Voltage, V
OUT
................
28 V
Reverse Output Voltage, V
OUT
........
-0.5 V
Continuous Output Current, I
OUT
...
25 mA
Operating Temperature Range, T
A
Suffix ‘E–’ .................
-40
°
C to +85
°
C
Suffix ‘L–’ ...............
-40
°
C to +150
°
C
Storage Temperature Range,
T
S
..............................
-65
°
C to +170
°
C
Always order by complete part number, e.g.,
A3121EUA
.
3121, 3122,
AND
3123
HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION
ELECTRICAL CHARACTERISTICS over operating temperature range, at V
CC
= 12 V.
Limits
Characteristic
Supply Voltage
Output Saturation Voltage
Output Leakage Current
Supply Current
Output Rise Time
Output Fall Time
Symbol
V
CC
V
OUT(SAT)
I
OFF
I
CC
t
r
t
f
Test Conditions
Operating
I
OUT
= 20 mA, B > B
OP
V
OUT
= 24 V, B < B
RP
B < B
RP
(Output OFF)
R
L
= 820
Ω,
C
L
= 20 pF
R
L
= 820
Ω,
C
L
= 20 pF
Min.
4.5
—
—
—
—
—
Typ.
—
140
<1.0
4.6
0.04
0.18
Max.
24
400
10
9.0
2.0
2.0
Units
V
mV
µA
mA
µs
µs
MAGNETIC CHARACTERISTICS in gauss over operating supply voltage range.
Part Numbers*
A3121
Characteristic
B
OP
at T
A
= 25°C
over operating temp. range
B
RP
at T
A
= 25°C
over operating temp. range
B
hys
at T
A
= 25°C
over operating temp. range
Min.
250
220
125
80
70
60
Typ.
350
350
245
245
105
105
Max.
450
500
380
410
140
150
Min.
280
260
140
120
70
70
A3122
Typ.
340
340
235
235
105
105
Max.
400
430
330
360
140
140
Min.
250
230
180
160
70
70
A3123
Typ.
345
345
240
240
105
105
Max
440
470
300
330
140
140
NOTES: Typical values are at T
A
= +25°C and V
CC
= 12 V.
B
OP
= operate point (output turns ON); B
RP
= release point (output turns OFF); B
hys
= hysteresis (B
OP
- B
RP
).
*Complete part number includes a suffix to identify operating temperature range (E- or L-) and package type ( -LT or -UA).
FUNCTIONAL BLOCK DIAGRAM
1
V
CC
REG.
X
3
OUTPUT
GROUND
2
Dwg. FH-005-2
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1992, 2002 Allegro MicroSystems, Inc.
3121, 3122,
AND
3123
HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION
TYPICAL OPERATING CHARACTERISTICS
SWITCH POINTS
400
OUTPUT SATURATION VOLTAGE
300
OPERATE POINT
I
OUT
= 20 mA
V
CC
= 4.5–24 V
SATURATION VOLTAGE IN mV
300
SWITCH POINT IN GAUSS
200
RELEASE POINT
200
V
CC
= 12 V
100
100
0
-50
-25
0
25
50
75
100
125
150
0
-50
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN
°
C
Dwg. GH-038
AMBIENT TEMPERATURE IN
°
C
Dwg. GH-040
SUPPLY CURRENT
7.0
SUPPLY CURRENT
10
V
CC
= 12 V
8.0
SUPPLY CURRENT IN mA
6.0
B
≥
B
OP
SUPPLY CURRENT IN mA
B
≥
B
OP
6.0
5.0
4.0
B
≤
B
RP
4.0
B
≤
B
RP
2.0
T
A
= +25°C
-50
-25
0
25
50
75
100
125
150
0
0
5
10
15
20
25
Dwg. GH-041
AMBIENT TEMPERATURE IN
°
C
Dwg. GH-039
SUPPLY VOLTAGE IN VOLTS
* Complete part number includes a suffix denoting operating temperature range (E- or L-) and package type ( -LT or -UA).
www.allegromicro.com
3
3121, 3122,
AND
3123
HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION
SENSOR LOCATIONS
(±0.005" [0.13 mm] die placement)
Suffix “LT”
ACTIVE AREA DEPTH
0.0305"
0.775 mm
NOM
0.089"
2.26 mm
OPERATION
The output of these devices (pin 3) switches low when the mag-
netic field at the Hall sensor exceeds the operate point threshold (B
OP
).
At this point, the output voltage is V
OUT(SAT)
. When the magnetic field
is reduced to below the release point threshold (B
RP
), the device output
goes high. 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 mechani-
cal vibration and electrical noise.
0.043"
1.09 mm
A
1
2
3
APPLICATIONS INFORMATION
Extensive applications information for Hall-effect sensors is
available in:
•
Hall-Effect IC Applications Guide,
Application Note 27701;
•
Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and
Lead Forming,
Application Note 27703.1;
•
Soldering of Through-Hole Hall-Sensor Dervices,
Application Note
27703; and
•
Soldering of Surface-Mount Hall-Sensor Devices,
Application Note
27703.2.
All are provided in
Allegro Electronic Data Book,
AMS-702. or at
Dwg. MH-008-2D
Suffix “UA”
ACTIVE AREA DEPTH
0.0195"
0.50 mm
NOM
0.082"
2.07 mm
www.allegromicro.com
A
BRANDED
SURFACE
1
2
3
0.055"
1.38 mm
Allegro
CHANGE IN OPERATE POINT
20
Dwg. MH-011-2D
CHANGE IN OPERATE POINT IN GAUSS
15
T
A
= +25°C
10
5.0
0
-5.0
0
5
10
15
20
25
Dwg. GH-042
SUPPLY VOLTAGE IN VOLTS
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3121, 3122,
AND
3123
HALL-EFFECT SWITCHES
FOR HIGH-TEMPERATURE
OPERATION
PACKAGE DESIGNATOR ‘LT’
(SOT89/TO-243AA)
Dimensions in Inches
(for reference only)
Dimensions in Millimeters
(controlling dimensions)
0.181
0.173
0.072
0.064
0.167
0.155
0.102
0.090
0.063
0.055
0.0173
0.0138
4.60
4.40
1.83
1.62
4.25
3.94
2.60
2.29
1.60
1.40
0.44
0.35
1
2
3
0.090
0.084
1
2
3
2.29
2.13
0.047
0.035
0.059
BSC
0.0189
0.0142
0.0221
0.0173
0.118
BSC
Dwg. MA-009-3A in
1.20
0.89
1.50
BSC
0.48
0.36
0.56
0.44
3.00
BSC
Dwg. MA-009-3A mm
0.098
0.079
B
A
0.031
0.102
0.181
3 0.047
0.031
TYP
2.5
2.0
B
A
0.8
2.6
4.6
1.2
0.8
TYP
1
0.028
TYP
2
1
0.7
TYP
2
3
Pads 1, 2, 3, and A — Standard SOT89 Layout
Pads 1, 2, 3, and B — Low-Stress Version
Pads 1, 2, and 3 only — Lowest Stress, But Not Self Aligning
Dwg. MA-012-3 in
Pads 1, 2, 3, and A — Standard SOT89 Layout
Pads 1, 2, 3, and B — Low-Stress Version
Pads 1, 2, and 3 only — Lowest Stress, But Not Self Aligning
Dwg. MA-012-3 mm
NOTES: 1. Exact body and lead configuration at vendor’s option within limits shown.
2. Supplied in bulk pack (500 pieces per bag) or add "TR" to part number for tape and reel.
3. Only low-temperature (≤240°C) reflow-soldering techniques are recommended for SOT89 devices.
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5
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