A1145 and A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: October 31, 2011
• for the A1145EUA-T use the
A1155LUA-T
• for the A1146EUA-T and the A1146LUA-T use the
A1156LUA-T
• for the A1145ELHLT-T use the
A1155LLHLX-T
• for the A1146ELHLT-T and the A1146LLHLT-T use the
A1156LLHLX-T
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
A1145 and A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Features and Benefits
▪
Chopper stabilization
▫
Low switchpoint drift over operating
temperature range
▫
Low sensitivity to stress
▪
Factory programmed at end-of-line for optimized
switchpoints
▪
On-chip protection
▫
Supply transient protection
▫
Reverse-battery protection
▫
On-board voltage regulator
▫
3.5 to 24 V operation
Description
The A1145 and A1146 devices are two-wire, unipolar, Hall
effect switches that are factory-programmed at end-of-line to
optimize ultrasensitive magnetic switchpoint accuracy.
These devices use a high frequency chopper-stabilization
technique, produced using the Allegro advanced BiCMOS
wafer fabrication process, to achieve magnetic stability and
to eliminate offset inherent in single-element devices exposed
to harsh application environments.
Commonly found in a number of automotive applications,
these switches are utilized in sensing seat track position, seat
belt buckle presence, hood/trunk latching, and shift selector
position. Two-wire unipolar switches, such as the A1145
and A1146, are particularly advantageous in price-sensitive
applications because they require one less wire for operation
than do switches with the more traditional open-collector output.
Additionally, the system designer inherently gains diagnostics
because there is always output current flowing, which should
be in either of two narrow ranges. Any current level not within
these ranges indicates a fault condition. These devices also
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
Continued on the next page…
Not to scale
V+
Functional Block Diagram
VCC
Regulator
To All Subcircuits
0.01 uF
Dynamic Offset
Cancellation
Clock/Logic
Sample and Hold
Low-Pass
Filter
Amp
GND
Package UA Only
GND
A1145-DS, Rev. 16
A1145
and
A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
field of sufficient strength, and switch HIGH otherwise.
Both versions are offered in two package styles. The LH is a SOT-
23W, miniature low-profile package for surface-mount applications.
The UA is a three-lead ultramini SIP for through-hole mounting.
Each package is available in a lead (Pb) free version (suffix,
–T)
with 100% matte tin plated leadframe. Field-programmable versions
also available: A1185 and A1186.
Description (continued)
feature on-chip transient protection and a Zener clamp to protect
against overvoltage conditions on the supply line.
The output currents of the A1146 switches HIGH in the presence
of a south (+) polarity magnetic field of sufficient strength, and
switches LOW otherwise, as in the presence of a weak field or a
north (–) polarity field. The A1145 has an opposite output: the
currents switch LOW in the presence of a south-polarity magnetic
Selection Guide
Part Number
A1145ELHLT-T
3
A1145EUA-T
4
A1146ELHLT-T
3
A1146EUA-T
4
A1146LLHLT-T
3
A1146LUA-T
4
1
Contact Allegro
2
South
Packing
1
Tape and Reel, 3000 pieces/reel
Bulk Bag, 500 pieces/bag
Tape and Reel, 3000 pieces/reel
Bulk Bag, 500 pieces/bag
Tape and Reel, 3000 pieces/reel
Bulk Bag, 500 pieces/bag
Package
Surface Mount
Through Hole
Surface Mount
Through Hole
Surface Mount
Through Hole
Operating Ambient
Temperature, T
A
(°C)
–40 to 85
–40 to 85
Output Level in
South (+) Field
2
Low
High
–40 to 150
for additional packing options.
(+) magnetic fields must be of sufficient strength.
3
This variant is in production, however, it has been deemed Pre-End of Life. The product is approaching end of life. Within a minimum of
6 months, the device will enter its final, Last Time Buy, order phase. Status change: January 31, 2011. Suggested replacements: for the
A1145ELHLT-T use the A1155LLHLX-T, for the A1146ELHLT-T and the A1146LLHLT-T use the A1156LLHLX-T.
4
Variant is in production but has been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of the variant is
currently restricted to existing customer applications. The variant should not be purchased for new design applications because obsoles-
cence in the near future is probable. Samples are no longer available. Status change: January 31, 2011.
Absolute Maximum Ratings
Characteristic
Supply Voltage
Reverse Supply Voltage
Magnetic Flux Density
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
CC
V
RCC
B
T
A
T
J
(max)
T
stg
Range E
Range L
Notes
Rating
28
–18
Unlimited
–40 to 85
–40 to 150
165
–65 to 170
Units
V
V
G
ºC
ºC
ºC
ºC
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A1145
and
A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Symbol
V
CC
I
CCL
I
CCH
I
RCC
V
ZSUPPLY
I
ZSUPPLY
di/dt
f
C
t
on
POS
C
BYPASS
= 0.01
μF
ELECTRICAL CHARACTERISTICS
over the operating voltage and temperature ranges, unless otherwise specified
Characteristic
Supply Voltage
1
Supply Current
2
Reverse Supply Current
Supply Zener Clamp Voltage
Supply Zener Clamp Current
3
Output Slew Rate
4
Chopping Frequency
Power-On Time
5
Power-On State
6,7
1
V
CC
represents
2
Relative values
Test Conditions
Min.
3.5
Typ.
–
–
–
–
–
–
36
200
–
HIGH
Max.
24
6.9
17
–1.6
40
9.9
–
–
25
–
Units
V
mA
mA
mA
V
mA
mA/μs
kHz
μs
–
B > B
OP
for A1145; B < B
RP
for A1146
B > B
OP
for A1146; B < B
RP
for A1145
V
RCC
= –18 V
I
CC
= I
CCL(max)
+ 3 mA; T
A
= 25°C
V
ZSUPPLY
= 28 V
Capacitance of the oscilloscope performing
the measurement = 20 pF
5
12
–
28
–
–
–
–
–
t < t
on
;
V
CC
slew rate > 25 mV/μs
the generated voltage between the VCC pin and the GND pin.
of B use the algebraic convention, where positive values indicate south magnetic polarity, and negative values indicate north magnetic
polarity; therefore greater B values indicate a stronger south polarity field (or a weaker north polarity field, if present).
3
I
ZSUPPLY(max)
= I
CCL(max)
+ 3 mA.
4
Measured without bypass capacitor between VCC and GND. Use of a bypass capacitor results in slower current change.
5
Measured with and without bypass capacitor of 0.01
μF.
Adding a larger bypass capacitor causes longer Power-On Time.
6
POS is defined as true only with a V
CC
slew rate of 25 mV /
μs
or greater. Operation with a V
CC
slew rate less than 25 mV /
μs
can permanently harm
device performance.
7
POS is undefined for t > t or B
on
RP
< B < B
OP
.
MAGNETIC CHARACTERISTICS
over the operating voltage and temperature ranges, unless otherwise specified
Characteristic
Operate Point
Symbol
B
OP
A1145
A1146
A1145
A1146
Test Conditions
I
CC
= I
CCL
I
CC
= I
CCH
I
CC
= I
CCH
I
CC
= I
CCL
Min.
20
Typ.*
37
Max.
60
Units
G
Release Point
Hysteresis
B
RP
B
HYS
10
5
22
15
55
30
G
G
B
HYS
= B
OP
– B
RP
*Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions, such as T
A
= 25°C and V
CC
= 12 V.
Performance may vary for individual units, within the specified maximum and minimum limits.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A1145
and
A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Characteristic Data
Supply Current (Low) versus Ambient Temperature
at Various Levels of V
CC
(A1145 and A1146)
10
8
Supply Current (High) versus Ambient Temperature
at Various Levels of V
CC
(A1145 and A1146)
20
18
V
CC
3.5 V
12.0 V
24.0 V
I
CCH
(mA)
I
CCL
(mA)
6
4
2
0
–50
16
14
12
10
–50
V
CC
3.5 V
12.0 V
24.0 V
0
50
100
150
200
0
50
100
150
200
Ambient Temperature, T
A
(°C)
Ambient Temperature, T
A
(°C)
Operate Point versus Ambient Temperature
at Various Levels of V
CC
(A1145 and A1146)
70
60
50
Switchpoint Hysteresis versus Ambient Temperature
at Various Levels of V
CC
(A1145 and A1146)
40
35
V
CC
B
HYS
(G)
3.5 V
12.0 V
24.0 V
30
25
20
15
10
5
V
CC
3.5 V
12.0 V
24.0 V
B
OP
(G)
40
30
20
10
0
–50
0
50
100
150
200
0
–50
0
50
100
150
200
Ambient Temperature, T
A
(°C)
Ambient Temperature, T
A
(°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
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