A1140, A1141, A1142, and A1143
Sensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Features and Benefits
▪
Chopper stabilization
▫
Low switchpoint drift over operating
temperature range
▫
Low sensitivity to stress
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Factory programmed at end-of-line for optimized
switchpoints
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On-chip protection
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Supply transient protection
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Reverse-battery protection
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On-board voltage regulator
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3.5 to 24 V operation
Description
The A1140, A1141, A1142, and A1143 devices are sensitive,
two-wire, unipolar, Hall effect switches that are factory-
programmed at end-of-line to optimize 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 to sense seat track position,
seat belt buckle presence, hood/trunk latching, and shift
selector position. Two-wire unipolar switches, such as the
A1140/41/42/43 family, 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. The A1140/41/42/43 family of switches also
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
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Not to scale
Functional Block Diagram
V+
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
A1140-DS, Rev. 8
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
