A1145 and A1146
Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Features and Benefits
▪
Chopper stabilization
▫
Low switchpoint drift over operating
temperature range
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Low sensitivity to stress
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Factory programmed at end-of-line for optimized
switchpoints
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On-chip protection
▫
Supply transient protection
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Reverse-battery protection
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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 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 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)
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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. 8
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
