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A1148EUA

P1-P3P4-P6P7-P9P10-P12
Description
The A1147 and A1148 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 patented 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 A1147
and A1148, 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
A1147-DS, Rev. 12
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
Low Current Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Continued on the next page…
Functional Block Diagram
Not to scale
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
A1147 and A1148
Amp
Regulator
Low-Pass
Filter
GND
VCC
GND
Package UA Only
0.01 uF
V+
Clock/Logic
Dynamic Offset
Cancellation
Sample and Hold
To All Subcircuits
Low Current Ultrasensitive Two-Wire
Chopper-Stabilized Unipolar Hall Effect Switches
A1147 and
A1148
2
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Selection Guide
Part Number Pb-Free Packing
1
Package
Operating Ambient
Temperature, T
A
(°C)
Output Level in
South (+) Field
2
A1147ELHLT-T Yes Tape and Reel, 3000 pieces/reel Surface Mount
–40 to 85
Low
A1147EUA-T Yes Bulk Bag, 500 pieces/bag Through Hole
A1147LLHLT-T Yes Tape and Reel, 3000 pieces/reel Surface Mount
–40 to 150
A1147LUA-T Yes Bulk Bag, 500 pieces/bag Through Hole
A1148ELHLT-T Yes Tape and Reel, 3000 pieces/reel Surface Mount
–40 to 85
High
A1148EUA-T Yes Bulk Bag, 500 pieces/bag Through Hole
A1148LLHLT-T Yes Tape and Reel, 3000 pieces/reel Surface Mount
–40 to 150
A1148LUA-T Yes Bulk Bag, 500 pieces/bag Through Hole
1
Contact Allegro for additional packing options.
2
South (+) magnetic fields must be of sufficient strength.
feature on-chip transient protection and a Zener clamp to protect
against overvoltage conditions on the supply line.
The output currents of the A1148 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 A1147 has an opposite output: the
currents switch LOW in the presence of a south-polarity magnetic
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: A1180 and A1181.
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Units
Supply Voltage V
CC
28 V
Reverse Supply Voltage V
RCC
–18 V
Magnetic Flux Density B Unlimited G
Operating Ambient Temperature T
A
Range E –40 to 85 ºC
Range L –40 to 150 ºC
Maximum Junction Temperature T
J
(max) 165 ºC
Storage Temperature T
stg
–65 to 170 ºC
Description (continued)
Low Current Ultrasensitive Two-Wire
Chopper-Stabilized Unipolar Hall Effect Switches
A1147 and
A1148
3
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
ELECTRICAL CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Supply Voltage
1
V
CC
3.5 – 24 V
Supply Current
2
I
CCL
B > B
OP
for A1147; B < B
RP
for A1148 2 – 5 mA
I
CCH
B > B
OP
for A1148; B < B
RP
for A1147 12 – 17 mA
Reverse Supply Current I
RCC
V
RCC
= –18 V – – –1.6 mA
Supply Zener Clamp Voltage V
ZSUPPLY
I
CC
= I
CCL(max)
+ 3 mA; T
A
= 25°C 28 – 40 V
Supply Zener Clamp Current
3
I
ZSUPPLY
V
ZSUPPLY
= 28 V – – 8 mA
Output Slew Rate
4
di/dt
Capacitance of the oscilloscope performing
the measurement = 20 pF
– 36 – mA/s
Chopping Frequency f
C
– 200 – kHz
Power-On Time
5
t
on
C
BYPASS
= 0.01 F
––25s
Power-On State
6,7
POS t < t
on
; V
CC
slew rate > 25 mV/s – HIGH – –
1
V
CC
represents the generated voltage between the VCC pin and the GND pin.
2
Relative values 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 F. 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 / s or greater. Operation with a V
CC
slew rate less than 25 mV / s can permanently harm
device performance.
7
POS is undefined for t > t
on
or B
RP
< B < B
OP
.
MAGNETIC CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic Symbol Test Conditions Min. Typ.* Max. Units
Operate Point B
OP
A1147 I
CC
= I
CCL
20 37 80 G
A1148 I
CC
= I
CCH
Release Point B
RP
A1147 I
CC
= I
CCH
10 22 60 G
A1148 I
CC
= I
CCL
Hysteresis B
HYS
B
HYS
= B
OP
– B
RP
51530G
*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.
P1-P3P4-P6P7-P9P10-P12

A1148EUA

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MAGNETIC SWITCH UNIPOLAR 3SIP
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