A1147 and A1148
A1147-DS, Rev. 6
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
AB SO LUTE MAX I MUM RAT INGS
Supply Voltage, V
CC
..........................................28 V
Reverse-Supply Voltage, V
RCC
........................–18 V
Magnetic Flux Density, B .........................Unlimited
Power Dissipation, P
D
............................ Graph, p. 5
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
On-chip protection
null Supply transient protection
null Reverse-battery protection
null On-board voltage regulator
null 3.5 to 24 V operation
Low Current Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Package LH, 3-pin SOT
Features and Benefits
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 tech-
nique, 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 latch-
ing, 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 diagnos-
tics 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 con-
dition. These devices also 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 oppo-
site 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 ultra-
mini 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.
Package UA, 3-pin SIP
Chopper stabilization
null Low switchpoint drift over operating
temperature range
null Low sensitivity to stress
Factory programmed at end-of-line for
optimized switchpoints
≈1:1
≈1:1