A1147 Datasheet, PDF (1/13 Pages) Allegro MicroSystems – Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches

A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized
Unipolar Hall Effect Switches
Package LH, 3-pin SOT
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.
≈1:1 _{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
Package UA, 3-pin SIP
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
≈1:1 ^{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.
ABSOLUTE MAXIMUM RATINGS
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
Features and Benefits
Chopper stabilization
Low switchpoint drift over operating
temperature range
Low sensitivity to stress
Factory programmed at end-of-line for
optimized switchpoints
On-chip protection
Supply transient protection
Reverse-battery protection
On-board voltage regulator
3.5 to 24 V operation
A1147-DS, Rev. 6
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com