Allegro A3046EU Hall effect gear-tooth sensors zero speed Datasheet

Data Sheet
27612A†
3046, 3056, AND
3058
HALL EFFECT GEAR-TOOTH SENSORS
–ZERO SPEED
X
X
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.
1
2
3
GROUND
OUTPUT
CC
SUPPLY
V
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 backbiasing 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.
Continued next page...
BENEFITS
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
■
■
■
■
■
■
■
■
■
Senses Ferrous Targets Down to Zero RPM
Large Effective Air Gap
Wide Operating Temperature Range
Operation from Unregulated Supply
High-Speed Operation
Output Compatible With All Logic Families
Reverse Battery Protection
Solid-State Reliability
Resistant to Physical Stress
SELECTION GUIDE
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
Switching Hysteresis
15-90 G
Operating Temp. Range
150-250 G
Device Type Number
-40°C to +85°C
A3046EU
A3056EU
A3058EU
-40°C to +150°C
A3046LU
A3056LU
A3058LU
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
All devices, when used with a backbiasing magnet, can be configured to turn ON
or OFF with the leading or trailing edge of a
gear tooth or slot. Changes in fields on the
magnet face caused by a moving ferrous
mass are sensed by two integrated Hall
transducers and are differentially amplified by
on-chip electronics. The on-chip temperature
compensation and Schmitt trigger circuitry
minimizes shifts in effective working air gaps
and switch points over temperature making
these devices ideal for use in ignition timing,
anti-lock braking systems, and speed measurement systems in hostile automotive and
industrial environments.
Each Hall effect digital Integrated circuit
includes two quadratic Hall effect sensing
elements, a voltage regulator, temperature
compensating circuitry, low-level amplifier,
Schmitt trigger, and an open-collector output
driver. The on-board regulator permits
operation with supply voltages of 4.5 to 24
volts. The output stage can switch up to 20
mA at conservatively specified repetition
rates to 20 kHz and is compatible with bipolar
and MOS logic circuits.
FUNCTIONAL BLOCK DIAGRAM
1
SUPPLY
REG
OUTPUT
3
+
–
X
2
X
GROUND
Dwg. FH-010
Both magnetic characteristics are available in a choice of two operating temperature ranges. Suffix EU devices have an operating range of
-40°C to +85°C while suffix LU devices feature an operating range of
-40°C to +150°C. All devices are packaged in a 3-pin plastic SIP.
ELECTRICAL CHARACTERISTICS at VCC = 8 V, over operating temperature range.
Limits
Characteristic
Symbol
Supply Voltage
VCC
Power-Up State
—
3058* only,
VCC = 0 4.5 V, B < BOP
VOUT(SAT)
IOUT = 20 mA, B > BOP
—
135
400
mV
Output Saturation Voltage
Test Conditions
Operating
Min.
Typ.
Max.
Units
4.5
—
24
V
Output is OFF
—
Output Leakage Current
IOFF
VCC = VOUT = 24 V, B < BRP
—
—
5.0
µA
Supply Current
ICC
VCC = 24 V, B < BRP
—
7.2
14
mA
Output Rise time
tr
RL = 820 Ω, CL = 20 pF
—
100
—
ns
Output Fall time
tf
RL = 820 Ω, CL = 20 pF
—
100
—
ns
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1989, 1995 Allegro MicroSystems, Inc.
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
MAGNETIC CHARACTERISTICS in gauss at VCC = 8 V.
Part Numbers*
3046
3056
3058
Min. Typ. Max.
Min. Typ. Max.
Min. Typ. Max.
Characteristic
Test Conditions
Operate Point, BOP
Output Switches OFF to ON,
TA = +25°C
—
—
150
—
—
150
—
—
250
Release Point, BRP
Output Switches ON to OFF,
TA = +25°C
-150
—
—
-150
—
—
-250
—
—
Hysteresis, Bhys
BOP-BRP, TA = +25°C
15
50
90
15
50
90
150 200 250
—
—
±50
—
—
±75
Over operating temperature range,
∆BOP or ∆BRP
Ref. BOP or BRP at TA = +25°C
NOTES: 1. Magnetic switch points are specified as the
difference in magnetic fields at the two Hall
elements.
2. As used here, negative flux densities are
defined as less than zero (algebraic convention).
3. Typical values are at TA = +25°C.
* Complete part number includes the prefix
‘A’ and a suffix to identify operating temperature range and package style. See selection
guide.
—
—
TYPICAL OPERATING CHARACTERISTICS
200
V =8V
CC
I OUT= 20 mA
180
SATURATION VOLTAGE IN mV
Change in Trip Point,
160
140
120
100
-50
0
50
100
AMBIENT TEMPERATURE IN °C
10
150
Dwg. GH-033
11
V CC= 24 V
TA = +25°C
10
B > BOP
SUPPLY CURRENT IN mA
SUPPLY CURRENT IN mA
9
8
B < BRP
7
6
9
B > B OP
8
7
B < BRP
6
5
0
5
10
15
20
25
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-031
www.allegromicro.com
5
-50
0
50
AMBIENT TEMPERATURE IN °C
100
150
Dwg. GH-032
±50
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
APPLICATIONS INFORMATION
Figure 1
TYPICAL GEAR-TOOTH SENSING
APPLICATION
BACK-BIASING
MAGNET
S
OPTIONAL POLE PIECE
Naming Conventions. With a south pole in front of the branded
surface of the sensor, a north pole behind the sensor, the field at the
sensor is defined as positive. As used here, negative flux densities are
defined as less than zero (algebraic convention), e.g., -100 G is less
than -50 G.
SENSOR IC
A
Magnet Biasing. In order to sense moving non-magnetized
ferrous targets, these devices must be back-biased by mounting the
unbranded side on a small permanent magnet. Either magnetic pole
(north or south) can be used.
S
The devices can also be used without a back-biasing magnet.
In this configuration, the sensor can be used to detect a rotating ring
magnet such as those found in brushless dc motors or in speed
sensing applications. Here, the sensor detects the magnetic field
gradient created by the magnetic poles.
TARGET
GEAR
Figure 2
TYPICAL TRANSFER CHARACTERISTIC
Dwg. AH-003
24 V
MAX
B OP
OUTPUT VOLTAGE IN VOLTS
N
A gear-tooth sensing system consists of the sensor IC, a backbiasing magnet, an optional pole piece, and a target (Figure 1). The
system requirements are usually specified in terms of the effective
working air gap between the package and the target (gear teeth), the
number of switching events per rotation of the target, temperature and
speed ranges, minimum pulse duration or duty cycle, and switch point
accuracy. Careful choice of the sensor IC, magnet material and
shape, target material and shape, and assembly techniques enables
large working air gaps and high switch-point accuracy over the system
operating temperature range.
B RP
V OUT(SAT)
0
-B
0
+B
DIFFERENTIAL FLUX DENSITY, BE1 – BE2
Dwg. GH-034
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
Sensor Operation. The A3046EU/LU,
A3056EU/LU, and A3058EU/LU sensor ICs
each contain two integrated Hall transducers
(E1 and E2) that are used to sense a magnetic field differential across the face of the
IC (see SENSOR LOCATION drawing). Referring
to Figure 2, the trigger switches the output
ON (output LOW) when BE1 – BE2 > BOP and
switches the output OFF (output HIGH) when
BE1 – BE2 < BRP. The difference between BOP
and BRP is the hysteresis of the device.
Figure 3 relates the output state of a
back-biased sensor IC, with switching
characteristics shown in Figure 2, to the
target gear profile and position. Assume a
north pole back-bias configuration (equivalent
to south pole at the face of the device). The
motion of the gear produces a phase-shifted
field at E1 and E2 (Figure 3 (a)); internal
conditioning circuitry subtracts the field at the
two elements (Figure 3 (b)); and the Schmitt
trigger at the output of the conditioning
circuitry switches at the pre-determined
thresholds (BOP and BRP). As shown (Figure
3 (c)), the IC output is LOW whenever sensor
E1 sees a (ferrous) gear tooth and sensor E2
faces air. The output is HIGH when sensor
E1 sees air and sensor E2 sees the ferrous
target.
Figure 3
GEAR-TOOTH SENSOR OPERATION
LEADING
EDGE
TRAILING
EDGE
GEAR
DIRECTION
OF ROTATION
E2
E1
NORTH
SOUTH
4300 G
(a)
B &B
E1
E2
4130 G
150 G
B OP= +25 G
(b)
B –B
E1
0G
E2
B RP= –25 G
-150 G
V
OUT
(c)
V
OUT(SAT)
OUTPUT DUTY CYCLE ≈ 50%
A gear-tooth sensor can be configured
(see ASSEMBLY TECHNIQUES) to operate as a
latch, a (positive) switch, or a negative
switch. Note the change in duty cycle in
each of the cases (Figure 4).
A latch is a device where the operate
point is greater than zero gauss and the
release point is less than zero gauss. With
the configuration shown in Figure 3, such a
device will switch ON on the leading edge
and OFF on the trailing edge of the target
tooth.
A (positive) switch is a device where
both the operate and release points are
greater than zero gauss (positive values).
www.allegromicro.com
Dwg. WH-003
In the configuration shown in Figure 3, such a device will switch ON
and then switch OFF on the leading or rising edge of the target tooth
(Figure 4 (a)).
A negative switch is a device where both the operate and release
points are less than zero gauss (negative values). In the configuration
shown in Figure 3, such a device will switch OFF and then switch ON
on the trailing or falling edge of the target tooth (Figure 4 (b)).
Speed sensors can use any of the three sensor configurations
described. Timing sensors, however, must use a latch to guarantee
dual-edge detection. Latches are most easily made using the
A3058EU or A3058LU device types.
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
SYSTEM ISSUES
Figure 4
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.
POSITIVE AND NEGATIVE SWITCH OPERATION
150 G
B OP= +100 G
B RP = +50 G
B –B
E1
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 0.32” diameter by
0.20” long (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-temperature performer; at temperatures above
E2
(a)
V
-150 G
OUT
V
OUT(SAT)
OUTPUT DUTY CYCLE = 65%
150 G
B –B
E1
E2
B OP = -50 G
B RP = -100 G
-150 G
(b)
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
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
Pole Piece Design. A pole piece may be used at the face of the
magnet to smooth out the magnet-face offsets. A 0.020” (0.51 mm)
thick, soft-iron pole piece will bring the field non-uniformity down to
the ±1%-to-±3% range. Note that pole pieces will minimize but not
eliminate the non-uniformity in the magnet face field. Front pole pieces
will almost always result in a reduced maximum air gap.
Figure 5
DIFFERENTIAL FLUX DENSITY
2000
DIFFERENTIAL FLUX DENSITY IN GAUSS
1500
1000
Ferrous Targets. The best ferrous targets are made of cold-rolled
low-carbon steel. Sintered-metal targets are also usable, but care
must be taken to ensure uniform material composition and density.
500
0
-500
The teeth or slots of the target should be cut with a slight angle
so as to minimize the abruptness of transition from metal to air as the
target passes by the sensor. Sharp transitions will result in magnetic
overshoots that can result in false triggering.
-1000
-1500
-2000
0
0.025
0.050
0.100
0.075
0.125
AIRGAP FROM PACKAGE FACE IN INCHES
Dwg. GH-035
200
100
50
ASSEMBLY TECHNIQUES
0
-50
-100
-150
-200
0.070
0.080
0.090
0.110
0.100
0.120
AIRGAP FROM PACKAGE FACE IN INCHES
Dwg. GH-036
SENSOR LOCATIONS
(±0.005” [0.13 mm] die placement)
ACTIVE AREA DEPTH
0.015"
0.38 mm
NOM
0.088"
2.23 mm
0.046"
1.17 mm
DIFFERENTIAL FLUX DENSITY IN GAUSS
150
Gear teeth larger than 0.10” (2.54 mm) wide and at least 0.10”
(2.54 mm) deep provide reasonable working air gaps and adequate
change in magnetic field for reliable switching. Generally, larger teeth
and slots allow a larger air gap. A gear tooth width approximating the
spacing between sensors (0.088” or 2.24 mm) requires special care in
the system design and assembly techniques.
0.075"
1.89 mm
E1
E2
A
BRANDED
SURFACE
1
2
3
Dwg. MH-002-8D
www.allegromicro.com
Due to magnet face non-uniformities and device variations, it is
recommended that applications requiring precision switching utilize a
mechanical optimization procedure during assembly. Without a pole
piece, the inherent magnet face offsets can be used to pre-bias the
magnetic circuit to obtain any desired operating mode. This is
achieved by physically changing the relative position of the magnet
behind the sensor to achieve the desired system performance objective. For example, with a rotating ABS gear, the objective might be a
50% duty cycle at maximum air gap. Similar objectives can be set for
ignition (crank and cam position) sensing systems.
Non-precision speed sensing applications do not require optimization. For applications where mechanical optimization is not feasible,
non-zero speed devices such as the UGN/UGS3059KA ac-coupled
gear-tooth sensor are available.
3046, 3056, AND 3058
HALL EFFECT
GEAR-TOOTH SENSORS
–ZERO SPEED
Dimensions in Inches
Dimensions in Millimeters
(controlling dimensions)
(for reference only)
0.183
0.178
4.65
4.52
0.063
0.059
1.60
1.50
0.181
0.176
4.60
4.47
45°
0.086
1
2
45°
0.018
3
2.18
1
2
0.46
3
MAX
MAX
15.24
14.23
0.0173
0.0138
0.600
0.560
0.44
0.35
0.48
0.36
0.0189
0.0142
SEE NOTE
SEE NOTE
1.27
2.54
0.050
0.100
Dwg. MH-003E mm
Dwg. MH-003E in
The products described herein are manufactured under one or
more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283;
5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719;
5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents
pending.
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such departures from the detail specifications as may be
required to permit improvements in the performance, reliability, or
manufacturability of its products. Before placing an order, the user is
cautioned to verify that the information being relied upon is current.
Allegro products are not authorized for use as critical components
in life-support appliances, devices, or systems without express written
approval.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of
third parties that may result from its use.
NOTES:1. Tolerances on package height and width represent
allowable mold offsets. Dimensions given are
measured at the widest point (parting line).
2. Exact body and lead configuration at vendor’s option
within limits shown.
3. Height does not include mold gate flash.
4. Recommended minimum PWB hole diameter to
clear transition area is 0.035” (0.89 mm).
5. Where no tolerance is specified, dimension is
nominal.
6. Minimum lead length was 0.500” (12.70 mm). If
existing product to the original specifications is not
acceptable, contact sales office before ordering.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000