A1185 and A1186
Ultrasensitive Two-Wire Field-Programmable
Chopper-Stabilized Unipolar Hall-Effect Switches
Features and Benefits
▪
Chopper stabilization
▫
Low switchpoint drift over operating
temperature range
▫
Low sensitivity to stress
▪
Field programmable for optimized switchpoints
▪
On-chip protection
▫
Supply transient protection
▫
Reverse-battery protection
▫
On-board voltage regulator
▫
3.5 to 24 V operation
Description
The A1185 and A1186 are ultrasensitive, two-wire, unipolar
Hall effect switches. The operate point, B
OP
, can be field-
programmed, after final packaging of the sensor and
placement into the application. This advanced feature allows
the optimization of the sensor switching performance, by
effectively accounting for variations caused by mounting
tolerances for the device and the target magnet.
This family of devices are produced on the Allegro
MicroSystems new DABIC5 BiCMOS wafer fabrication
process, which implements a patented, high-frequency, chopper-
stabilization technique that achieves magnetic stability and
eliminates the offsets that are inherent in single-element devices
exposed to harsh application environments. Commonly found
in a number of automotive applications, the A1185 and A1186
devices are utilized to sense: seat track position, seat belt buckle
presence, hood/trunk latching, and shift selector position.
Two-wire unipolar switches are particularly advantageous
in price-sensitive applications, because they require one less
wire than the more traditional open-collector output switches.
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
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Not to scale
Functional Block Diagram
V+
VCC
Program/Lock
Programming
Logic
Offset
Adjust
Regulator
Clock/Logic
0.01 uF
Sample and Hold
Dynamic Offset
Cancellation
Low-Pass
Filter
To all
subcircuits
Amp
GND
Package UA Only
GND
A1185-DS, Rev. 2
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
