ATS612JSB: Dynamic, Self-Calibrating, Peak-Detecting, Differential Hall-Effect Gear-Tooth Sensor IC

ATS612LSB
Dynamic, Self-Calibrating, Peak-Detecting,
Differential Hall Effect Gear Tooth Sensor IC
Discontinued Product
These parts are no longer in production The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: April 28, 2007
Recommended Substitutions:
For existing customer transition, and for new customers or new applications, refer to the ATS617LSG.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. 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 which may result from its use.
Data Sheet
27627.110 b
ATS612LSB
DYNAMIC, SELF-CALIBRATING,
PEAK-DETECTING, DIFFERENTIAL
HALL-EFFECT GEAR-TOOTH SENSOR IC
4
3
2
The ATS612LSB gear-tooth sensor IC is a peak detecting device that
uses automatic gain control to provide extremely accurate gear edge
detection down to low operating speeds. Each package consists
of a high-temperature plastic shell that holds together a samariumcobalt pellet, a pole piece, and a differential open-collector Hall IC
that has been optimized to the magnetic circuit. This small package
can be easily assembled and used in conjunction with a wide variety of
gear shapes and sizes.
1
Pin 1 = Supply
Pin 2 = Output
Pin 3 = Capacitor
Pin 4 = Ground
Dwg. AH-006
ABSOLUTE MAXIMUM RATINGS
over operating temperature range
Supply Voltage, VCC ............................... 24 V*
Reverse Supply Voltage, V RCC .............. -16 V
Output OFF Voltage, VOUT ....................... 24 V
Continuous Output Current, I OUT ...... 25 mA†
Reverse Output Current, I ROUT ............ 50 mA
Package Power Dissipation,
PD .......................................... See Graph
The technology used for this device is Hall-effect
based. The device incorporates a dual-element Hall IC that switches in
response to differential magnetic signals created by ferrous targets.
The sophisticated processing circuitry contains a 5-bit A/D converter
that self-calibrates (normalizes) the internal gain of the device to
minimize the effect of air-gap variations. The patented peak-detecting
filter circuit eliminates magnet and system offsets and has the ability to
discriminate relatively fast changes such as those caused by tilt, gear
wobble, and eccentricities yet provides stable operation to extremely
low RPM.
These devices are ideal for use in gathering speed, position, and timing information using gear-tooth-based configurations. The
ATS612LSB is particularly suited to those applications that require
extremely accurate duty cycle control or accurate edge detection such
as in automotive crank shaft applications. The lower vibration sensitivity also makes this device extremely useful for transmission speed
sensing applications.
ATS612LSB: Large/small-tooth gear-position sensing —
crank angle, transmission speed, cam angle.
continued next page…
Operating Temperature Range,
TA ................................. -40°C to +150°C*
Storage Temperature, T S .................. +170°C
* Operation at increased supply voltages with
external circuitry is described in Applications
Information. Devices for operation at increased
temperatures are available on special order.
† Output is current limited at 25 mA to 55 mA.
Continued operation in this mode can cause
excessive device heating and failure. See graph,
next page.
Always order by complete part number: ATS612LSB .
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
FEATURES AND BENEFITS
Fully Optimized Differential Digital Gear-Tooth Sensor IC
Single-Chip Sensing IC for High Reliability
Digital Output Representing Target Profile
Extremely Low Timing Accuracy Drift with Temperature
Large Operating Air Gaps
Small Mechanical Size
Optimized Magnetic Circuit
Patented Peak-Detecting Filter:
80 µs Typical Power-On Time
<10 RPM Operation (single-tooth target)
Correct First-Edge Detection
Uses Small Value Ceramic Capacitors
■ Under-Voltage Lockout
■ Wide Operating Voltage Range
■ Defined Power-On State
■
■
■
■
■
■
■
■
ALLOWABLE PACKAGE POWER DISSIPATION IN mW
1000
800
RθJA = 150°C/W
600
400
200
0
20
40
60
80
100
120
140
AMBIENT TEMPERATURE IN °C
FUNCTIONAL BLOCK DIAGRAM
SUPPLY
REG
POWER-ON
LOGIC
UVLO
GAIN
X
E1
MAGNET
X
E2
+
–
REFERENCE
GENERATOR
1
OUTPUT
TRACK &
HOLD
+
–
CURRENT
LIMIT
3
CAPACITOR
Dwg. FH-014-1
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 2001, 2002 Allegro MicroSystems, Inc.
2
GROUND
4
160
180
Dwg. GH-065-7
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
ELECTRICAL CHARACTERISTICS over operating voltage and temperature range,
C3 = 0.1 µF to 0.47 µF.
Characteristic
Symbol
Supply Voltage
Power-On State
Limits
Typ. Max.
Test Conditions
Min.
Units
VCC
Operating, TJ < 165°C
3.6
–
24
V
POS
VCC = 0 → 5 V
HIGH
HIGH
HIGH
–
Under-Voltage Lockout
VCC(UV)
VCC = 0 → 5 V
2.5
–
3.6
V
Under-Voltage Hysteresis
VCC(hys)
VCC(UV) – VCC(SD)
–
0.2
–
V
Low Output Voltage
VOUT(SAT)
IOUT = 20 mA
–
190
400
mV
Output Current Limit
IOUTM
VOUT = 12 V
25
45
55
mA
Output Leakage Current
IOFF
VOUT = 24 V
–
0.2
15
µA
Supply Current
ICC
Output OFF
6.0
8.2
13
mA
Output ON
8.0
10
15
mA
Power-On Delay
ton
VCC > 5 V
–
80
500
µs
Output Rise Time
tr
RL = 500 Ω, CL = 10 pF
–
0.2
5.0
µs
Output Fall Time
tf
RL = 500 Ω, CL = 10 pF
–
0.2
5.0
µs
NOTES: Typical data is at VCC = 8 V and TA = +25°C and is for design information only.
VCC(SD) = shutdown voltage, VCC = 5 V → 0.
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3
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
OPERATION over operating voltage and temperature range with reference target
(unless otherwise specified).
Characteristic
Symbol
Air Gap Range
Limits
Typ. Max.
Test Conditions
Min.
AG
Operating,
Target Speed > 20 RPM
0.4
–
2.5
mm
Calibration Cycle
ncal
Output edges before which
calibration is completed*
1
1
1
Edge
Calibration Mode
Disable
ndis
Output falling edges for startup
calibration to be complete
64
64
64
Edges
Timing Accuracy
tθ
Target Speed = 1000 RPM,
0.4 mm ≤ AG ≤ 2 mm
–
±0.5
±0.75
°
* Non-uniform magnetic profiles may require additional output pulses before calibration is completed.
h
t =5
mm
REFERENCE TARGET
Do = 120 mm
TARGET
F (THICKNESS) ≥ 3 mm
3
m
T=
3m
m
m
E1
AIR GAP
E2
IC
POLE PIECE
SOUTH
RARE EARTH
PELLET
SIGNATURE
TOOTH (1)
NORTH
1
4
2
3
4
Dwg. MH-016-2 mm
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Units
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
TYPICAL ELECTRICAL CHARACTERISTICS
14
13
12
12
11
SUPPLY CURRENT IN mA
OUTPUT ON
10
9.0
V
=8V
CC
8.0
OUTPUT OFF
7.0
4.0
-40
OUTPUT ON
10
9.0
8.0
OUTPUT OFF
7.0
T = 25°C
A
6.0
6.0
0
40
80
5.0
200
160
120
2.0
6.0
AMBIENT TEMPERATURE IN ° C
10
14
18
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-058-1
Dwg. GH-014-2
275
OUTPUT SATURATION VOLTAGE IN mV
SUPPLY CURRENT IN mA
11
250
I
= 20 mA
OUT
225
200
175
150
-40
0
40
80
120
160
200
AMBIENT TEMPERATURE IN °C
Dwg. GH-013-2
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5
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
TYPICAL OPERATING CHARACTERISTICS
(with reference target)
2.0
2.0
1.6
1000 RPM
LEADING TARGET EDGE
RELATIVE ACCURACY IN DEGREES
RELATIVE ACCURACY IN DEGREES
1000 RPM
TRAILING TARGET EDGE
-40°C
+25°C
+150°C
1.2
0.8
0.4
0
0
0.5
1.0
1.5
2.0
2.5
AIR GAP IN MILLIMETERS
1.6
1.2
0.8
0.4
0
3.0
-40°C
+25°C
+150°C
0
0.5
Dwg. GH-008-7
2.0
2.5
3.0
Dwg. GH-008-8
1.6
SIGNATURE TOOTH
10 RPM
LEADING TARGET EDGE
RELATIVE ACCURACY IN DEGREES
RELATIVE ACCURACY IN DEGREES
SIGNATURE TOOTH
10 RPM
TRAILING TARGET EDGE
-40°C
+25°C
+150°C
1.2
0.8
0.4
0
0.5
1.0
1.5
2.0
AIR GAP IN MILLIMETERS
6
1.5
2.0
2.0
0
1.0
AIR GAP IN MILLIMETERS
2.5
3.0
Dwg. GH-008-6
1.6
-40°C
+25°C
+150°C
1.2
0.8
0.4
0
0
0.5
1.0
1.5
2.0
AIR GAP IN MILLIMETERS
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
2.5
3.0
Dwg. GH-008-5
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
TYPICAL OPERATING CHARACTERISTICS
(with reference target) — Continued
1.0
2.0
PERIODIC TOOTH
1000 RPM
LEADING TARGET EDGE
RELATIVE ACCURACY IN DEGREES
0.8
RELATIVE ACCURACY IN DEGREES
PERIODIC TOOTH
1000 RPM
TRAILING TARGET EDGE
-40°C
+25°C
+150°C
0.6
0.4
0.2
0
0
0.5
1.0
1.5
2.0
2.5
0.8
0.4
4.0
4.0
3.5
3.0
2.5
-40°C
+25°C
+150°C
1.5
0
10
20
30
40
50
REFERENCE TARGET SPEED IN RPM
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0.5
Dwg. GH-008-10
4.5
1.0
0
60
70
Dwg. GH-011-4
1.0
1.5
2.0
2.5
AIR GAP IN MILLIMETERS
4.5
2.0
-40°C
+25°C
+150°C
1.2
0
3.0
MAXIMUM AIR GAP IN MILLIMETERS
MAXIMUM AIR GAP IN MILLIMETERS
AIR GAP IN MILLIMETERS
1.6
3.0
Dwg. GH-008-9
3.5
3.0
2.5
-40°C
+25°C
+150°C
2.0
1.5
1.0
0
500
1000
1500
REFERENCE TARGET SPEED IN RPM
2000
2500
Dwg. GH-011-3
7
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
DEVICE DESCRIPTION
The use of this device is simple; after correct power
is applied to the component, it is capable of instantly
providing digital information that is representative of the
profile of a rotating gear. No additional optimization or
processing circuitry is required. This ease of use should
reduce design time and incremental assembly costs for
most applications.
Hall Technology . This ATS612 package
contains a single-chip differential Hall-effect sensor IC, a
samarium-cobalt pellet, and a flat ferrous pole piece.
The Hall IC consists of two Hall elements located so as to
measure the magnetic gradient created by the passing of a
ferrous object (a gear). The two elements measure the
field gradient and convert it to voltage which is then
subtracted and processed in order to provide a digital
output signal.
The processing circuit uses a patented peak detection scheme to eliminate magnet and system offsets. This
technique allows dynamic coupling and filtering of offsets
without the power-up and settling time disadvantages of
classical high-pass filtering schemes. The peak signal of
every tooth and valley is detected by the filter and is used
to provide an instant reference for the operate and release
point comparator. In this manner, the thresholds are
adapted and referenced to individual signal peaks and
valleys, hence providing immunity to zero line variation
due to installation inaccuracies (tilt, rotation, and off center
placement), as well as for variations caused by target and
shaft eccentricities. The peak detection concept also
allows extremely low speed operation for small value filter
capacitors.
8
DIFFERENTIAL
MAGNETIC FLUX
OPERATE
OPERATE
0
RELEASE
RELEASE
V
BB
OUTPUT
The ATS612LSB gear-tooth sensor IC is a Hall
IC/pellet configuration that is fully optimized to provide
digital detection of gear-tooth edges in a small package
size. This device contains self-calibrating circuitry that
nulls out the effect of air gap variations on the switching
accuracy of the device. A high startup hysteresis minimizes false switching caused by magnetic overshoot. The
device is packaged in a miniature plastic housing that has
been optimized for size, ease of assembly, and
manufacturability. High operating temperature materials
are used in all aspects of construction.
V
OUT(SAT)
Dwg. WH-011
The ATS612LSB also includes self-calibration
circuitry that is engaged at power on. The signal amplitude is measured and the device gain is normalized. In
this manner, switch-point drift versus air gap is minimized
and excellent timing accuracy can be achieved. The AGC
circuitry, in conjunction with a unique hysteresis circuit,
also eliminates the effect of gear edge overshoot as well
as increases the immunity to false switching caused by
gear tooth anomalies at close air gap. The AGC circuit
sets the gain of the device after power on. Up to 0.25 mm
air gap change can occur after calibration is complete
without significant performance impact.
Superior Performance. The ATS612LSB peak-detecting
differential gear-tooth sensor IC has several advantages over conventional Hall-effect gear-tooth sensors.
The signal-processing techniques used in the ATS612LSB
peak-detecting differential gear-tooth sensor IC solve the
catastrophic issues that affect the functionality of conventional digital gear-tooth sensors.
• Temperature drift. Changes in temperature do not
greatly affect this device due to the stable amplifier
design and the offset rejection circuitry.
• Timing accuracy variation due to air gap. The
accuracy variation caused by air gap changes is
minimized by the self calibration circuitry. A 2x-to-3x
improvement can be seen.
• Dual edge detection. Because this device switches
from the positive and negative peaks of the signal, dual
edge detection is guaranteed.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
DEVICE DESCRIPTION — Continued
•
•
•
•
Differential vs. Single-Element Design . The differential
Hall-element configuration is superior in most applications
to the classical single-element gear-tooth sensor. As
shown in the flux maps on this page, the
single-element configuration commonly used (Hall-effect
sensor mounted on the face of a simple permanent
magnet) requires the detection of a small signal (often
<100G) that is superimposed on a large back-biased field,
often 1500G to 3500G. For most gear/target configurations, the back-biased field values change due to concentration effects, resulting in a varying baseline with air gap,
with valley widths, with eccentricities, and with vibration.
The differential configuration cancels the effects of the
back-biased field and avoids many of the issues presented
by the single Hall element.
TARGET
SINGLE ELEMENT MAGNETIC FIELD IN GAUSS
•
Tilted or off-center installation. Traditional differential sensors will switch incorrectly due to baseline
changes versus air gap caused by tilted or off center
installation. The peak detector circuitry references the
switch point from the peak and is immune to this failure
mode. There may be a timing accuracy shift caused by
this condition.
Large operating air gaps. Operating air gaps greater
than 2.5 mm are easily achievable (dependent on target
dimensions, material, and speed) with this device due
to the sensitive switch points after start up.
Immunity to magnetic overshoot. The air gapindependent hysteresis minimizes the impact of overshoot on the switching of device output.
Response to surface defects in the target. The gainadjust circuitry reduces the effect of minor gear anomalies that would normally cause false switching.
Immunity to vibration and backlash. The gain-adjust
circuitry keeps the hysteresis of the device roughly
proportional to the peak to peak signal. This allows the
device to have good immunity to vibration even when
operating at close air gaps.
Immunity to gear run out. The differential element
configuration eliminates the base line variations caused
by gear run out.
T
A
= 25°C
-2000
-2500
AIR GAP = 2.5 mm
AIR GAP = 2.0 mm
-3000
AIR GAP = 1.5 mm
-3500
AIR GAP = 1.0 mm
-4000
AIR GAP = 0.5 mm
-4500
-5000
0
10
20
30
40
50
60
ANGLE OF TARGET ROTATION IN DEGREES
Dwg. GH-061-1
Single-element flux maps
showing the impact of varying valley widths
TARGET
DIFFERENTIAL MAGNETIC FIELD IN GAUSS
•
T
A
= 25°C
1500
AIR GAP = 0.5 mm
1000
AIR GAP = 1.0 mm
500
0
AIR GAP = 2.5 mm
AIR GAP = 2.0 mm
AIR GAP = 1.5 mm
-500
-1000
-1500
0
10
20
30
40
50
60
ANGLE OF TARGET ROTATION IN DEGREES
Differential flux maps vs. air gaps
Dwg. GH-061
NOTE — 10 G = 1 mT, exactly.
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9
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
DEVICE DESCRIPTION — Continued
Peak-Detecting vs. AC-Coupled Filters. High-pass
filtering (normal ac coupling) is a commonly used technique for eliminating circuit offsets. AC coupling has errors
at power on because the filter circuit needs to hold the
circuit zero value even though the circuit may power on
over a large signal. Such filter techniques can only
perform properly after the filter has been allowed to settle,
which is typically greater than one second. Also,
high-pass filter solutions cannot easily track rapidly
changing baselines such as those caused by eccentricities. Peak detection switches on the change in slope of
the signal and is baseline independent at power up and
during running.
Peak Detecting vs. Zero-Crossing Reference. The
usual differential zero-crossing sensors are susceptible to
false switching due to off-center and tilted installations,
which result in a shift in baseline that changes with air gap.
The track-and-hold peak-detection technique ignores
baseline shifts versus air gaps and provides increased
immunity to false switching. In addition, using
track-and-hold peak-detecting techniques, increased air
gap capabilities can be expected because a peak detector
utilizes the entire peak-to-peak signal range as compared
10
to zero-crossing detectors that switch on one-half the
peak-to-peak signal.
NOTE — “Baseline” refers to the zero-gauss differential
where each Hall-effect element is subject to the same
magnetic field strength.
Power-On Operation. The device will power on in the
OFF state (output high) irrespective of the magnetic field
condition. The power-up time of the circuit is no greater
than 500 µs. The circuit is then ready to accurately detect
the first target edge that results in a HIGH-to-LOW transition.
Under-Voltage Lockout. When the supply voltage is
below the minimum operating voltage (VCC(UV)), the
device is OFF and stays OFF irrespective of the state of
the magnetic field. This prevents false signals, which may
be caused by under-voltage conditions (especially during
turn on), from appearing at the output.
Output. The device output is an open-collector stage
capable of sinking up to 20mA. An external pull-up
(resistor) to a supply voltage of not more than 24V must
be supplied.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
CRITERIA FOR DEVICE QUALIFICATION
All Allegro devices are subjected to stringent qualification requirements prior to being released to production. To
become qualified, except for the destructive ESD tests, no failures are permitted.
Qualification Test
Test Method and
Test Conditions
Test Length
Samples
Per Lot
Temperature Humidity
Bias Life
JESD22-A101,
TA = 85°C, RH = 85%
1000 hrs
77
Bias Life
JESD22-A108,
TA = 150°C, TJ = 165°C
1000 hrs
77
(Surge Operating Life)
JESD22-A108,
TA = 175°C, TJ = 190°C
168 hrs
77
Autoclave, Unbiased
JESD22-A102,
TA = 121°C, 15 psig
96 hrs
77
High-Temperature
(Bake) Storage Life
JESD22-A103,
TA = 170°C
1000 hrs
77
Temperature Cycle
JESD22-A104
1000 cycles
77
ESD,
Human Body Model
CDF-AEC-Q100-002
Pre/Post
Reading
3 per
test
Comments
Device biased for
minimum power
-55°C to +150°C
Test to failure
Pin 3 > 1.5 kV
All other pins > 3 kV
GEAR/TARGET SYSTEM EVALUATION*
An analog map of the magnetic signal can be
obtained by measuring the voltage at pin 3 (the capacitor
pin) while the device is running. The peak and valley hold
voltage will represent the peak-to-peak value of the signal.
More accurate measurements can be taken by connecting
an extremely small capacitor (0.05 µF) from pin 3 to
ground. After the device is powered up and has switched
at least 64 times, a 1 kΩ bleed-off resistor should be
installed in parallel with the capacitor without powering
down the device. If the gear is then rotated at an extremely low speed, an analog representation of the gain-
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adjusted signal can be measured at pin 3. Note that the
device should be re-powered at each air gap and the
above procedure repeated for accurate measurements. In
both cases, the analog signal may be compared to the
typical hysteresis of the device and device performance
can be estimated.
* In application, the terms “gear” and “target” are often
interchanged. However, “gear” is preferred when motion
is transferred.
11
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
APPLICATIONS INFORMATION
Recommended Evaluation Technique. The selfcalibrating feature of the ATS612LSB requires that a
special evaluation technique be used to measure its highaccuracy performance capabilities. Installation inaccuracies are calibrated out at power on only; hence, it is
extremely important that the device be re-powered at each
air gap when gathering timing accuracy data.
Self-Calibrating Functions. The ATS612LSB is designed to minimize performance variation caused by the
large air gap variations resulting from installation by selfcalibrating at power-on. This function should be tested
using the following procedure.
1. Set the air gap to the desired value.
2. Power down and then power on the device.
3. Rotate the target at the desired speed.
4. Wait for calibration to complete (64 output pulses to
occur).
5. Monitor output for correct switching and measure
accuracy.
6. Repeat the above for multiple air gaps within the
operating range of the device.
7. This can be repeated over the entire operating temperature range.
Measurement of the effect of changing air gap after power
on:
1. Set the air gap to the desired value (nominal, for
example). Rotate the target at the desired speed.
Apply power to the package. Wait for 64 output pulses
to occur. Monitor output for correct switching and
measure accuracy.
Gear Diameter and Pitch. Signal frequency is a direct
function of gear pitch and rotational speed (RPM). The
width of the magnetic signal in degrees and, hence, the
signal slope created by the tooth is directly proportional to
the circumference of the gear (πDo). Smaller diameters
limit the low-speed operation due to the slower rate of
change of the magnetic signal per degree of gear rotation
(here the limitation is the droop of the capacitor versus the
signal change). Larger diameters limit high-speed operation due to the higher rate of change of magnetic signal
per degree of rotation (here the limitation is the maximum
charge rate of the capacitor versus the rate of signal
change). These devices are optimized for a 50mm gear
diameter (signal not limited by tooth width), 0.22 µF
capacitor, and speeds of 10 RPM to 8000 RPM. For very
large diameter gears (diameter >200 mm), the devices
must be configured with a lower value capacitor, but not
less than 0.1 µF. This allows for a range of 5:1 in gear
diameters.
Air Gap and Tooth Geometry. Operating specifications
are impacted by tooth width (T), valley width (pc - T) and
depth (ht), gear material, and gear face thickness (F). The
target can be a gear or a specially cut shaft-mounted tone
wheel made of stamped ferrous metal. In general, the
following gear or target guidelines must be followed to
achieve greater than 2mm air gap from the face of unit:
Tooth width, T .............................. >2 mm
Valley width, pc - T ...................... >2 mm
(Whole) depth, ht ......................... >3 mm
Gear material ............................... low-carbon steel
Gear face width (thickness), F ..... >3 mm
Deviation from these guidelines will result in a
reduction of air gap and a deterioration in timing accuracy.
2. Change the air gap by ± 0.25 mm. Do not re-power
device. Monitor the output for correct switching and
measure accuracy.
12
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
APPLICATIONS INFORMATION — Continued
to pin 4), the output of the device will switch from LOW to
HIGH as the leading edge of the target passes the package,
which means that the output will be HIGH when the unit is
facing a tooth.
4
3
2
1
2.235 COS α (mm)
0.088 COS α (inch)
Operation with Fine-Pitch gears. For targets with a
circular pitch of less than 4mm, a performance improvement can be observed by rotating the front face of the
package. This rotation decreases the effective
element-to-element spacing and increases the capability of
detecting fine tooth or valley configurations, provided that
the Hall elements are not rotated beyond the width of the
target.
2.235 mm
0.088"
α
TARGET FACE WIDTH, F
>2.235 SIN α (mm)
>0.088 SIN α (inch)
A
A
Dwg. AH-006-1
Dwg. MH-018-1
Signal Timing Accuracy. The magnetic field profile width
is defined by the element spacing and narrows in
degrees as the target diameter increases. This results in
improved timing accuracy performance for larger gear
diameters (for the same number of gear teeth).
Valley-to-tooth transistions will generally provide better
accuracy than tooth-to-valley transitions for large-tooth or
large-valley configurations. For highest accuracy, targets
greater than 100mm in diameter should be used.
Signal Duty Cycle. For repetitive target structures,
precise duty cycle is maintained over the operating air gap
and temperature range due to an extremely good symmetry in the magnetic switch points and the internal self
calibration of the device. For irregular tooth geometries,
there will be a small but measureable change in pulse
width versus air gap.
Output Polarity. The output of the device will switch from
HIGH to LOW as the leading edge of the target passes the
package in the direction indicated below (pin 4 to pin 1),
which means that the output will be LOW when the unit is
facing a tooth. If rotation is in the opposite direction (pin 1
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Power Supply Protection. The IC contains an onchip voltage regulator and can operate over a wide supply
voltage range. For devices that need to operate from an
unregulated power supply, transient protection should be
added externally. For applications using a regulated
supply, external EMI/RFI protection is often required.
Insufficient protection can result in unexplained pulses on
the output line, providing inaccurate sensing information to
the user.
The filter capacitor and EMI protection circuitry can
easily be added to a PC board for use with these devices.
Provisions have been made for simple mounting of a
board on the back of the unit.
4
3
2
1
Dwg. AH-007
13
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
APPLICATIONS INFORMATION — Continued
Operation From a Regulated Power Supply. These
devices require minimal protection circuitry during operation from a low-voltage regulated line. The on-chip voltage
regulator provides immunity to power supply variations
between 3.6V and 24V. However, even while operating
from a regulated line, some supply and output filtering is
required to provide immunity to coupled and injected noise
on the supply line. A basic RC low-pass circuit (R1C1) on
the supply line and an optional output capacitor (C2) is
recommended for operation in noisy environments.
Because the device has an open-collector output, an
output pull-up resistor (RL) must be included either at the
IC output (pin 2) or by the signal processor input.
OUTPUT
SUPPLY
C2
100 pF
RL
20 Ω
R1
2.5 kΩ
RZ
C1
0.033 µF
0.22 µF
C3
6.8 V
0.033 µF
CS
1
2
3
X
X
4
Vcc
SUPPLY
OUTPUT
C2
100 pF
RL
20 Ω
R1
sufficiently high reverse breakdown capabilities so as to
withstand the most negative transient. The current-limiting
resistor (RZ) and the Zener diode should be sized for
power dissipation requirements.
C1
0.033 µF
+
-
0.22 µF
C3
1
2
Dwg. EH-008A
4
3
Vcc
X
X
Capacitor Requirements. The choice of the capacitor at
pin 3 (C3) defines the minimum operating speed of the
target. This capacitor (0.1 µF minimum) is required to
stabilize the internal amplifiers as well as to eliminate the
signal offsets. Typically, a 0.22 µF low-leakage ceramic
capacitor is recommended. Values greater than 0.47 µF
should not be used as this may cause high-speed performance degradation.
+
-
Dwg. EH-008-1A
Operation From an Unregulated Power Supply. In
automotive applications, where the device receives its
power from an unregulated supply such as the battery, full
protection is generally required so that the device can
withstand the many supply-side transients. Specifications
for such transients vary between car manufacturers, and
protection-circuit design should be optimized for each
application. In the circuit below, a simple Zener-controlled
regulator is constructed using discrete components. The
RC low-pass filter on the supply line (R1C1) and a lowvalue supply bypass capacitor (CS) can be included, if
necessary, so as to minimize susceptibility to EMI/RFI.
The npn transistor should be chosen with sufficiently high
forward breakdown voltage so as to withstand supply-side
transients. The series diode should be chosen with
14
Capacitor leakage current at pin 3 will cause degradation in the low-speed performance of the device. Excess capacitor leakage can result in the IC changing
output state without movement of the gear tooth being
sensed. In addition to the capacitor leakage, it is extremely important to minimize the leakage at the PC board
and between the pins of the device. Up to 50nA of
external leakage can be tolerated at the capacitor pin node
to ground. Choice of low-leakage-current potting compounds and the use of clean PC board techniques are
extremely important.
Additional applications Information on gear-tooth
and other Hall-effect devices is provided in the Allegro
Integrated and Discrete Semiconductors Data Book or
Application Note 27701.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
MECHANICAL INFORMATION
Component
Material
Function
Units
170
°C*
Package Face
Thermoset epoxy
Maximum temperature
Plastic Housing
Thermoplastic PBT,
30% glass filled
264 psi deflection temp. (DTUL)
66 psi deflection temp. (DTUL)
Approximate melting temperature
204°C
216°C
225°C
Flame Class Rating
—
—
UL94V-0
Leads
Copper
—
—
Lead Finish
90/10 tin/lead solder plate
—
†
Lead Pull
—
—
8N
*Temperature excursions to 225 °C for 2 minutes or less are permitted.
†All industry-accepted soldering techniques are permitted for these packages provided the indicated maximum temperature for each component (e.g., package face, plastic housing) is not exceeded. Reasonable dwell times, which do not
cause melting of the plastic housing, should be used.
Element Location (in millimeters)
(Element location relative to package center is the design objective)
Lead Cross Section (in millimeters)
2.235
1.1
0.48
0.36
0.41
NOM.
0.1
0.38
0.44
0.35
NOM.
A
0.0076
MIN. PLATING
THICKNESS
Dwg. MH-018 mm
Dwg. MH-019A mm
Allegro
www.allegromicro.com
15
ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR IC
DIMENSIONS IN MILLIMETERS
1.27
8.8
7.0
TYP
1
2
3
7.0
4
0.41
0.38
3.9
3.0 NOM
A
0.9 DIA
8.09
2.0
8.96
Dwg. MH-017-1B mm
Tolerances, unless otherwise specified: 1 place ±0.1 mm, 2 places ±0.05 mm.
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.
16
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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