A1140/41/42/43
Sensitive Two-Wire Chopper-Stabilized
Unipolar Hall-Effect Switches
The A1140, A1141, A1142, and A1143 devices are sensitive, two-wire, unipo-
lar, Hall effect switches that are factory-programmed at end-of-line to optimize
magnetic switchpoint accuracy. These devices are produced on the Allegro
MicroSystems advanced 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 A1140-43 family of 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 appli-
cations, because they require one less wire than the more traditional open-collec-
tor output switches. Additionally, the system designer gains inherent diagnostics
because output current normally
fl
ows in either of two narrowly-specified ranges.
Any output current level outside of these two ranges is a fault condition. The
A1140-43 family of devices also features on-chip transient protection, and a Zener
clamp to protect against overvoltage conditions on the supply line.
The output currents of the A1141 and A1143 switch
HIGH
in the presence of a south
polarity magnetic
fi
eld of sufficient strength; and switch
LOW
otherwise, including
when there is no significant magnetic
fi
eld present. The A1140 and A1142 have
inverted output current levels: switching
LOW
in the presence of a south polarity
magnetic
fi
eld of sufficient strength, and
HIGH
otherwise. The devices also differ in
their specified
LOW
current supply levels.
All family members are offered in two package styles: SOT-23W, a miniature low-
profile package for surface-mount applications (suffix
–LH),
and TO-92, three-
lead ultra-mini Single Inline Package (SIP) for through-hole mounting
(suffix
–UA).
Field-programmable versions are also available. Refer to: A1180, A1181, A1182,
and A1183.
Package LH, 3-pin SOT
3
1. VCC
2. No connection
3. GND
NC
1
2
Package UA, 3-pin SIP
1. VCC
2. GND
3. GND
1
2
PTCT
3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
..........................................
28 V
Reverse-Supply Voltage, V
RCC
........................
–18 V
Magnetic Flux Density, B .........................Unlimited
Operating Temperature
Ambient, T
A
, Range E..................
–40ºC to 85ºC
Ambient, T
A
, Range L................
–40ºC to 150ºC
Maximum Junction, T
J(max)
........................165ºC
Storage Temperature, T
S
..................
–65ºC to 170ºC
Features and Benefits
Chopper stabilization
Low switchpoint drift over operating tem-
perature range
Low stress sensitivity
Factory programmed at end-of-line for
optimized switchpoints
On-chip protection
Supply transient protection
Reverse-battery protection
On-board voltage regulator
3.5 V to 24 V operation
A1140-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
