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3046 Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer 3046
Beschreibung HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 8 Seiten
3046 Datasheet, Funktion
3046, 3056, AND
3058
HALL EFFECT GEAR-TOOTH SENSORS
–ZERO SPEED
XX
V
CC
12
3
Dwg. PH-012
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC . . . . . . . . . . . . . . 28 V
Reverse Battery Voltage,
VRCC . . . . . . . . . . . . . . . . . . . . . . -30 V
Magnetic Flux Density, B . . . . . Unlimited
Output OFF Voltage, VOUT . . . . . . . . . 28 V
Reverse Output Voltage, VOUT . . . . . -0.5 V
Output Current, IOUT . . . . . . . . . . . . 25 mA
Package Power Dissipation, PD . . 500 mW
Operating Temperature Range, TA
Suffix “EU” . . . . . . . . . -40°C to +85°C
Suffix “LU” . . . . . . . . -40°C to +150°C
Storage Temperature Range,
TS . . . . . . . . . . . . . . . -65°C to +170°C
The A3046EU/LU, A3056EU/LU, and A3058EU/LU Hall effect
gear-tooth sensors are monolithic integrated circuits that switch in
response to differential magnetic fields created by ferrous targets.
These devices are ideal for use in gear-tooth-based speed, position,
and timing applications and operate down to zero rpm over a wide
range of air gaps and temperatures. When combined with a back-
biasing magnet and proper assembly techniques, devices can be
configured to give 50% duty cycle or to switch on either leading,
trailing, or both edges of a passing gear tooth or slot.
The six devices differ only in their magnetic switching values and
operating temperature ranges. The low hysteresis of the A3046/56EU
and A3046/56LU makes them perfectly suited for ABS (anti-lock brake
system) or speed sensing applications where maintaining large air
gaps is important. The A3046EU/LU features improved switch point
stability with temperature over the A3056EU/LU. The high hysteresis
of the A3058EU and A3058LU, with their excellent temperature
stability, makes them especially suited to ignition timing applications
where switch-point accuracy (and latching requirements) is extremely
important.
Continued next page...
BENEFITS
I Senses Ferrous Targets Down to Zero RPM
I Large Effective Air Gap
I Wide Operating Temperature Range
I Operation from Unregulated Supply
I High-Speed Operation
I Output Compatible With All Logic Families
I Reverse Battery Protection
I Solid-State Reliability
I Resistant to Physical Stress
SELECTION GUIDE
Operating Temp. Range
-40°C to +85°C
-40°C to +150°C
Switching Hysteresis
15-90 G
150-250 G
Device Type Number
A3046EU
A3056EU
A3058EU
A3046LU
A3056LU
A3058LU






3046 Datasheet, Funktion
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
SYSTEM ISSUES
Optimal performance of a gear-tooth
sensing system strongly depends on four
factors: the IC magnetic parameters, the
magnet, the pole piece configuration, and
the target.
Sensor Specifications. Shown in
Figure 5 are graphs of the differential field as
a function of air gap. A 48-tooth, 2.5
(63.5 mm) diameter, uniform wheel similar to
that used in ABS applications is used. The
samarium cobalt magnet is 0.32diameter by
0.20long (8.13 x 5.08 mm). The maximum
functioning air gap with this typical gear/
magnet combination can be determined
using the graphs and the specifications for
the sensor IC.
In this case, if an A3056EU/LU sensor
with a BOP of +25 G and a BRP of -25 G is
used, the maximum allowable air gap would
be 0.110(2.79 mm). If the switch points
change +75 G with temperature (BOP = + 100
G, BRP = +50 G), the maximum air gap will be
approximately 0.077(1.96 mm).
All system issues should be translated
back to such a profile to aid the prediction of
system performance.
Magnet Selection. These devices can
be used with a wide variety of commercially
available permanent magnets. The selection
of the magnet depends on the operational
and environmental requirements of the
sensing system. For systems that require
high accuracy and large working airgaps or
an extended temperature range, the usual
magnet material of choice is rare earth
samarium cobalt (SmCo). This magnet
material has a high energy product and can
operate over an extended temperature range.
For systems that require low-cost solutions
for an extended temperature range, Alnico-8
can be used. Due to its relatively low energy
product, smaller operational airgaps can be
expected. At this time, neodymium iron
boron (NeFeB) is not a proven high-tempera-
ture performer; at temperatures above
Figure 4
POSITIVE AND NEGATIVE SWITCH OPERATION
150 G
B B
E1 E2
B OP= +100 G
B RP= +50 G
(a) -150 G
V
OUT
V
OUT(SAT)
OUTPUT DUTY CYCLE = 65%
150 G
B B
E1 E2
(b)
BOP= -50 G
B RP= -100 G
-150 G
V
OUT
V
OUT(SAT)
OUTPUT DUTY CYCLE = 33%
Dwg. WH-004
+150°C it may irreversibly lose magnetic strength. Of these three
magnet materials, Alnico-8 is the least expensive by volume and
SmCo is the most expensive.
Either cylindrical- or cube-shaped magnets can be used, as long
as the magnet pole face at least equals the facing surface(s) of the IC
package and the pole piece. Choose the length of the magnet to
obtain a high length-to-width ratio, up to 0.75:1 for rare earths, or 1.5:1
for Alnico-8. Any added magnet length may incrementally improve the
allowable maximum air gap.
Magnets, in general, have a non-uniform magnetic surface profile.
The flux across the face of a magnet can vary by as much as 5% of the
average field over a 0.10(2.5 mm) region. If a Hall sensor is placed
directly on a magnet face, the non-uniformity can appear to shift the
operating parameters of the sensor. For example, if a device is placed
on a 3000 G magnet with ±2% face offsets, each of the operating
points might be shifted by ±60 G. When offsets are present, the
operating characteristics may be greatly altered.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

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