Allegro ATS625LSGTN-T True zero-speed low-jitter high accuracy gear tooth sensor Datasheet

ATS625LSG
True Zero-Speed Low-Jitter
High Accuracy Gear Tooth Sensor
Features and Benefits
Description
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The ATS625 true zero-speed gear tooth sensor is an optimized
Hall IC and magnet configuration packaged in a molded module
that provides a manufacturer-friendly solution for digital gear
tooth sensing applications. The sensor assembly consists of an
over-molded package that holds together a samarium cobalt
magnet, a pole piece concentrator, and a true zero-speed Hall
IC that has been optimized to the magnetic circuit. This small
package can be easily assembled and used in conjunction with
gears of various shapes and sizes.
Highly repeatable over operating temperature range
Tight timing accuracy over operating temperature range
True zero-speed operation
Air-gap–independent switchpoints
Vibration immunity
Large operating air gaps
Defined power-on state
Wide operating voltage range
Digital output representing target profile
Single-chip sensing IC for high reliability
The sensor incorporates a dual-element Hall IC that switches
in response to differential magnetic signals created by a ferrous
target. Digital processing of the analog signal provides zerospeed performance independent of air gap as well as dynamic
adaptation of device performance to the typical operating
conditions found in automotive applications (reduced vibration
sensitivity). High-resolution peak detecting DACs are used to
set the adaptive switching thresholds of the device. Switchpoint
hysteresis reduces the negative effects of any anomalies in
the magnetic signal associated with the targets used in many
automotive applications. This sensor system is optimized
Continued on the next page…
Package: 4 pin SIP (suffix SG)
Continued on the next page…
Not to scale
Functional Block Diagram
V+
VCC
Voltage
Regulator
Automatic
Gain
Control
0.1 F
CBYPASS
Hall
Amp
PDAC
Threshold
Comparator
PPeak
PThresh
VPROC
Threshold
Logic
Reference
Generator
NDAC
NThresh
NPeak
Current
Limit
GND
AUX
(Recommended)
ATS625LSG-DS, Rev. 2
Output
Transistor
VOUT
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Features and Benefits (continued)
▪ Small mechanical size
▪ Optimized Hall IC magnetic system
▪ Fast start-up
▪ AGC and reference adjust circuit
▪ Undervoltage lockout
Selection Guide
Part Number
ATS625LSGTN-T3
Description (continued)
for crank applications that utilize targets that possess signature
regions.
TheATS625 is provided in a 4-pin SIP. The Pb (lead) free
option, available by special request, has a 100% matte tin plated
leadframe.
Pb-free1
Yes
Packing2
Tape and Reel 13-in. 800 pcs./reel
1Pb-based
variants are being phased out of the product line. Certain variants cited in this footnote are in production but have
been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to
existing customer applications. The device should not be purchased for new design applications because obsolescence in the
near future is probable. Samples are no longer available. Status change: May 1, 2006. These variants include: ATS625LSGTN
2Contact Allegro for additional packing options.
3Some restrictions may apply to certain types of sales. Contact Allegro for details.
Absolute Maximum Ratings
Characteristic
Symbol
Supply Voltage
VCC
Reverse-Supply Voltage
VRCC
Notes
See Power Derating section
Rating
Units
26.5
V
–18
V
Reverse-Supply Current
IRCC
50
mA
Reverse-Output Voltage
VROUT
–0.5
V
Output Sink Current
IOUT
10
mA
–40 to 150
ºC
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Operating Ambient Temperature
TA
Maximum Junction Temperature
Storage Temperature
Pin-out Diagram
Range L
Terminal List
Name
VCC
VOUT
1
2
3
4
Description
Connects power supply to chip
Number
1
Output from circuit
2
AUX
For Allegro use only
3
GND
Ground
4
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Operating Characteristics Valid at TA = –40°C to 150°C, TJ ≤ TJ(max), over full range of AG, unless otherwise noted; typical
operating parameters: VCC = 12 V and TA = 25°C
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
4.0
–
24
V
–
–
< VCC(min)
V
ELECTRICAL CHARACTERISTICS
Supply Voltage
VCC
Undervoltage Lockout
Operating; TJ < TJmax
VCCUV
Reverse Supply Current
IRCC
VCC = –18 V
–
–
–10
mA
Supply Zener Clamp Voltage1
VZ
ICC = 17 mA
28
–
–
V
Supply Zener Current2
IZ
VS = 28 V
–
–
17
mA
Output OFF
–
8.5
14
mA
Output ON
–
8.5
14
mA
–
High
–
V
–
–
200
μs
Supply Current
ICC
POWER-ON CHARACTERISTICS
Power-On State
SPO
Power-On Time
tPO
Gear Speed < 100 RPM; VCC > VCC min
OUTPUT STAGE
Low Output Voltage
VOUT(SAT) ISINK = 20 mA, Output = ON
–
200
450
mV
Output Current Limit
IOUT(LIM)
VOUT = 12 V, TJ < TJmax
25
45
70
mA
Output Leakage Current
IOUT(OFF)
Output = OFF, VOUT = 24 V
–
–
10
μA
Output Rise Time
tr
RL = 500 Ω, CL = 10 pF
–
1.0
2
μs
Output Fall Time
tf
RL = 500 Ω, CL = 10 pF
–
0.6
2
μs
S
Reference target 60+2
0
–
12000
rpm
Corresponds to switching frequency – 3 dB
–
20
–
kHz
–
60
–
%
–
40
–
%
–
1
6
edges
SWITCHPOINT CHARACTERISTICS
Speed
Bandwidth
BW
Operate Point
BOP
Release Point
BRP
% of peak-to-peak signal, AG < AGmax;
BIN transitioning from LOW to HIGH
% of peak-to-peak signal, AG < AGmax;
BIN transitioning from HIGH to LOW
CALIBRATION
Initial Calibration3
CalPO
Calibration Update
Cal
Start-up
Running mode operation
continuous
–
Continued on the next page...
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Operating Characteristics, continued Valid at TA = –40°C to 150°C, TJ ≤ TJ(max), over full range of AG, unless otherwise noted;
typical operating parameters: VCC = 12 V and TA = 25°C
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
0.5
–
2.5
mm
OPERATING CHARACTERISTICS with 60+2 reference target
Operational Air Gap
Relative Timing Accuracy, Sequential Mechanical Rising Edges
Relative Timing Accuracy, Sequential Mechanical Falling Edges
Relative Timing Accuracy, Signature Mechanical Rising Edge4
Relative Timing Accuracy, Signature Mechanical Falling Edge5
AG
Measured from sensor branded face to
target tooth
ERRRR
Relative to measurement taken at
AG = 1.5 mm
–
–
±0.4
deg.
ERRFF
Relative to measurement taken at
AG = 1.5 mm
–
–
±0.4
deg.
ERRSIGR
Relative to measurement taken at
AG = 1.5 mm
–
–
±0.4
deg.
ERRSIGF
Relative to measurement taken at
AG = 1.5 mm
–
–
±1.5
deg.
Relative Repeatability, Sequential
Rising and Falling Edges6
TθE
360° Repeatability, 1000 edges; peak-peak
sinusoidal signal with BPEAK ≥ BIN(min) and
6° period
–
–
0.08
deg.
Operating Signal7
BIN
AG(min) < AG < AG(max)
60
–
–
G
1
Test condition is ICC(max) + 3 mA.
2 Upper limit is I
CC(max) + 3 mA.
3 Power-on speed ≤ 200 rpm. Refer to the Sensor Description section for information on start-up behavior.
4 Detection accuracy of the update algorithm for the first rising mechanical edge following a signature region can be adversely affected by the magnetic
bias of the signature region. Please consult with Allegro field applications engineering for aid with assessment of specific target geometries.
5 Detection accuracy of the update algorithm for the falling edge of the signature region is highly dependent upon specific target geometry. Please consult
with Allegro field applications engineering for aid with assessment of specific target geometries.
6 The repeatability specification is based on statistical evaluation of a sample population.
7 Peak-to-peak magnetic flux strength required at Hall elements for complying with operational characteristics.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Reference Target (Gear) Information
REFERENCE TARGET 60+2
Characteristics
Symbol
Test Conditions
Typ.
Units
120
mm
Do
Outside diameter of target
Face Width
F
Breadth of tooth, with respect
to sensor
6
mm
Circular Tooth Length
t
Length of tooth, with respect
to sensor; measured at Do
3
mm
Signature Region Circular Tooth Length
tSIG
Length of signature tooth,
with respect to sensor; measured at Do
15
mm
Circular Valley Length
tv
Length of valley, with respect
to sensor; measured at Do
3
mm
Tooth Whole Depth
ht
3
mm
–
–
Material
Low Carbon Steel
Branded Face
of Sensor
tV
t,t
SI
G
Outside Diameter
Symbol Key
ØDO
F
ht
Air Gap
Signature Region
Pin 4
Pin 1
Branded Face
of Sensor
Reference Target
60+2
Figure 1. Configuration with Radial-Tooth Reference Target
For the generation of adequate magnetic field levels, the following recommendations should be followed in the design and
specification of targets:
• 2 mm < tooth width, t < 4 mm
• Valley width, tv > 2 mm
• Valley depth, ht > 2 mm
• Tooth thickness, F ≥ 3 mm
• Target material must be low carbon steel
Although these parameters apply to targets of traditional
geometry (radially oriented teeth with radial sensing, shown in
figure 1), they also can be applied in applications using stamped
targets (an aperture or rim gap punched out of the target material) and axial sensing. For stamped geometries with axial sensing, the valley depth, ht, is intrinsically infinite, so the criteria for
tooth width, t, valley width, tv, tooth material thickness, F, and
material specification need only be considered for reference. For
example, F can now be < 3 mm.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Characteristic Data: Electrical
ICC(ON) Versus TA
14
14
13
13
Vcc = 26.5V
12
12
Vcc = 20V
11
Vcc = 12V
10
Vcc = 4V
TA (°C)
11
-40
0
25
85
150
10
9
8
7
Current (mA)
Current (mA)
ICC(ON) Versus VCC
9
8
6
5
0
5
10
15
20
25
5
-50
30
-25
0
25
50
75
100
125
150
175
Temperature (°C)
Voltage (V)
ICC(OFF) Versus VCC
ICC(OFF) Versus TA
14
14
13
13
Vcc = 24V
12
12
Vcc = 20V
11
Vcc = 12V
10
Vcc = 4V
TA (°C)
11
-40
0
25
85
150
10
9
8
7
Current (mA)
Current (mA)
26.5
20.0
12.0
4.0
7
6
VCC (V)
24.0
20.0
12.0
4.0
9
8
7
6
6
5
5
0
5
10
15
20
25
-50
30
-25
0
Voltage (V)
25
50
75
100
125
150
175
Temperature (°C)
IOUT(OFF) Versus TA
VOUT(SAT) Versus TA
10
400
8
350
6
300
4
VOUT (V)
2
26.5
20.0
12.0
4.0
0
-2
-4
Voltage (mV)
Current (uA)
VCC (V)
IOUT (mA)
25
20
15
10
5
250
200
150
100
-6
50
-8
0
-10
-50
-25
0
25
50
75
100
Temperature (°C)
125
150
175
-50
-25
0
25
50
75
100
125
150
175
Temperature (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Characteristic Data: Relative Timing Accuracy
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient
Signature Tooth Rising Edge
Signature Tooth Rising Edge
0.5 mm Air Gap
0.5 mm Air Gap
1.5
1.0
1.0
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
-1.0
-1.5
0
500
1000
1500
2000
Edge Position (°)
Edge Position (°)
1.5
S (rpm)
0.5
0.0
-0.5
-1.0
-1.5
-50
2500
0
Target Speed, S (rpm)
100
150
200
Relative Timing Accuracy Versus Ambient
Signature Tooth Falling Edge
0.5 mm Air Gap
Signature Tooth Falling Edge
0.5 mm Air Gap
1.5
1.5
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
Edge Position (°)
1.0
1.0
S (rpm)
50
100
500
1000
1500
2000
0.5
0.0
-0.5
-1.0
-1.0
-1.5
-50
-1.5
0
500
1000
1500
2000
2500
0
Target Speed, S (rpm)
50
100
150
Temperature, TA (°C)
200
Relative Timing Accuracy Versus Ambient
Relative Timing Accuracy Versus Speed
Rising Edge Following Signature Tooth
Rising Edge Following Signature Tooth
0.5 mm Air Gap
0.5 mm Air Gap
1.5
1.5
1.0
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
-1.0
-1.5
0
500
1000
1500
2000
Target Speed, S (rpm)
2500
Edge Position (°)
Edge Position (°)
50
Temperature, TA (°C)
Relative Timing Accuracy Versus Speed
Edge Position (°)
50
100
500
1000
1500
2000
1.0
S (rpm)
0.5
50
100
500
1000
1500
2000
0.0
-0.5
-1.0
-1.5
-50
0
50
100
150
200
Temperature, TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient
Signature Tooth Rising Edge
Signature Tooth Rising Edge
2.5 mm Air Gap
2.5 mm Air Gap
1.5
1.0
1.0
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
-1.0
-1.5
0
500
1000
1500
2000
Edge Position (°)
Edge Position (°)
1.5
S (rpm)
0.5
0.0
-0.5
-1.0
-1.5
-50
2500
0
Target Speed, S (rpm)
100
150
200
Relative Timing Accuracy Versus Ambient
Signature Tooth Falling Edge
2.5 mm Air Gap
Signature Tooth Falling Edge
2.5 mm Air Gap
1.5
1.5
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
Edge Position (°)
1.0
1.0
S (rpm)
50
100
500
1000
1500
2000
0.5
0.0
-0.5
-1.0
-1.0
-1.5
-50
-1.5
0
500
1000
1500
2000
2500
0
Target Speed, S (rpm)
50
100
150
Temperature, TA (°C)
200
Relative Timing Accuracy Versus Ambient
Relative Timing Accuracy Versus Speed
Rising Edge Following Signature Tooth
Rising Edge Following Signature Tooth
2.5 mm Air Gap
2.5 mm Air Gap
1.5
1.5
1.0
TA (°C)
0.5
–40
0
25
85
150
0.0
-0.5
-1.0
-1.5
0
500
1000
1500
2000
Target Speed, S (rpm)
2500
Edge Position (°)
Edge Position (°)
50
Temperature, TA (°C)
Relative Timing Accuracy Versus Speed
Edge Position (°)
50
100
500
1000
1500
2000
1.0
S (rpm)
0.5
50
100
500
1000
1500
2000
0.0
-0.5
-1.0
-1.5
-50
0
50
100
150
200
Temperature, TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Relative Timing Accuracy Versus Air Gap
Relative Timing Accuracy Versus Air Gap
Signature Tooth Rising Edge
Signature Tooth Falling Edge
TA = –40, 0, 25, 85, 150 (°C)
S = 50, 100, 500, 1000, 1500, 2000 (rpm)
Edge Position (°)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
0.5
1.0
1.5
2.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
3.0
0.0
0.5
Air Gap (mm)
1.0
1.5
2.0
Air Gap (mm)
2.5
3.0
Relative Timing Accuracy Versus Air Gap
Rising Edge Following Signature Tooth
TA = –40, 0, 25, 85, 150 (°C)
S = 50, 100, 500, 1000, 1500, 2000 (rpm)
Edge Position (°)
0.0
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
0
0.5
1.0
1.5
2.0
2.5
3.0
Air Gap (mm)
Characteristic Data: Repeatability
360° Repeatability Versus Air Gap
Sequential Tooth Falling Edge
S = 1000 rpm
0.25
TA (°C)
Repeatabilty (°)
Edge Position (°)
TA = –40, 0, 25, 85, 150 (°C)
S = 50, 100, 500, 1000, 1500, 2000 (rpm)
0.20
–40
25
150
0.15
0.10
0.05
0
0
1.0
2.0
3.0
4.0
Air Gap (mm)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
9
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Sensor Description
the magnetic gradient created by the passing of a ferrous object.
This is illustrated in figures 2 and 3. The differential output of
the two elements is converted to a digital signal that is processed
to provide the digital output.
Assembly Description
The ATS625LSG true zero-speed gear tooth sensor is a combined Hall IC-magnet configuration that is fully optimized to
provide digital detection of gear tooth edges. This sensor is
integrally molded into a plastic body that has been optimized for
size, ease of assembly, and manufacturability. High operating
temperature materials are used in all aspects of construction.
Switching Description
After proper power is applied to the component, the sensor is
then capable of providing digital information that is representative of the profile of a rotating gear, as illustrated in figure 4.
No additional optimization is needed and minimal processing
circuitry is required. This ease of use reduces design time and
incremental assembly costs for most applications.
Sensing Technology
The gear tooth sensor contains a single-chip differential Hall
effect sensor IC, a 4-pin leadframe, a samarium cobalt magnet,
and a flat ferrous pole piece. The Hall IC consists of two Hall
elements spaced 2.2 mm apart, and each independently measures
Target (Gear)
Element Pitch
Hall Element 2
Dual-Element
Hall Effect Device
South Pole
Branded Face
of Sensor
Rotating Target
Hall Element 1
Hall IC
Pole Piece
(Concentrator)
1
Back-biasing Magnet
North Pole
(Pin n >1 Side)
Plastic
(Pin 1 Side)
Figure 3. This left-to-right (pin 1 to pin 4) direction of target rotation
results in a high output signal when a tooth of the target gear is centered
over the face of the sensor. A right-to-left (pin 4 to pin 1) rotation inverts
the output signal polarity.
Figure 2. Device Cross Section. Relative motion of the target is detected
by the dual Hall elements mounted on the Hall IC. This view is from the
side opposite the pins.
Target
Mechanical Profile
Target
Magnetic Profile
4
Signature Tooth
B+
BIN
Sensor Output
Switch State
On
Off
On
Off
On
Off
On
Off
On
Off
On Off On Off On Off
V+
Sensor Output
Electrical Profile
Target Motion from
Pin 1 to Pin 4
VOUT
Sensor Output
Electrical Profile
Target Motion from
Pin 4 to Pin 1
VOUT
V+
Figure 4. The magnetic profile reflects the geometry of the target, allowing the device to present an accurate digital output response.
10
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
figure 5 is the basic configuration required for proper device
operation. Contact Allegro field applications engineering for
information on the circuitry required for compliance to various
EMC specifications.
Undervoltage Lockout
When the supply voltage falls below the undervoltage lockout
level, VCCUV, the device switches to the OFF state. The device
remains in that state until the voltage level is restored to to the
VCC operating range. Changes in the target magnetic profile
have no effect until voltage is restored. This prevents false signals caused by undervoltage conditions from propagating to the
output of the sensor.
Internal Electronics
The ATS625LSG contains a self-calibrating Hall effect IC
that possesses two Hall elements, a temperature compensated
amplifier and offset cancellation circuitry. The IC also contains
a voltage regulator that provides supply noise rejection over the
operating voltage range. The Hall transducers and the electronics are integrated on the same silicon substrate by a proprietary
BiCMOS process. Changes in temperature do not greatly affect
this device due to the stable amplifier design and the offset rejection circuitry.
Power Supply Protection
The device contains an on-chip regulator and can operate over
a wide range of supply voltage levels. For applications using an
unregulated power supply, transient protection must be added
externally. For applications using a regulated supply line, EMI
and RFI protection may still be required. The circuit shown in
VS
1
VCC
CBYPASS
0.1 µF 3
RPU
ATS625
AUX
VOUT
2
Sensor Output
GND
4
Figure 5. Power Supply Protection Typical Circuit
11
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS625LSG
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
Sensor Operation Description
Power-On State
At power-on, the device is guaranteed to initialize in the OFF
state, with VOUT high.
First Edge Detection
The device uses the first two mechanical edges to synchronize
with the target features (tooth or valley) and direction of rotation
of the target. The device is synchonized by the third edge. The
actual behavior is affected by: target rotation direction relative to
Sensor
Pin 4 Side
the, target feature (tooth, rising edge, falling edge, or valley) that
is centered on the device at power-on, and fact that the sensor
powers-on in the OFF state,with VOUT high, regardless of the
eventual direction of target rotation. The interaction of these factors results in a number of possible power-on scenarios. These
are diagrammed in figure 6. In all start-up scenarios, the correct
number of output edges is provided, but the accuracy of the first
two edges may be compromised.
Target Motion Relative to Sensor
Sensor
Pin 1 Side
Target Mechanical Profile
Target Magnetic Profile
Sensor Output, VOUT
(Start-up over valley)
(A) Target relative movement
as shown in figure 3. Output
signal is high over the tooth.
(Start-up over rising edge)
(Start-up over tooth)
(Start-up over falling edge)
Sensor start-up location
Sensor
Pin 1 Side
Target Motion Relative to Sensor
Sensor
Pin 4 Side
Target Mechanical Profile
Target Magnetic Profile
(B) Target relative movement
opposite that shown in figure 3.
Output signal is low over the tooth.
Sensor Output, VOUT
(Start-up over valley)
(Start-up over rising edge)
(Start-up over tooth)
(Start-up over falling edge)
Sensor start-up location
Figure 6. Start-up Position And Relative Motion Effects on First Device Output Switching. Panel A shows the effects when the
target is moving from pin 1 toward pin 4 of the device; VOUT goes high at the approach of a tooth. When the target is moving
in the opposite direction, as in panel B, the polarity of the device output inverts; VOUT goes low at the approach of a tooth.
12
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
AGC (Automatic Gain Control)
The AGC feature is implemented by a unique patented selfcalibrating circuitry. After each power-on, the device measures
the peak-to-peak magnetic signal. The gain of the sensor is then
Differential Electrical Signal versus Target Rotation
at Various Air Gaps, Without AGC
adjusted, keeping the internal signal amplitude constant over the
air gap range of the device, AG. This feature ensures that operational characteristics are isolated from the effects of changes in
AG. The effect of AGC is shown in figure 7.
Differential Electrical Signal versus Target Rotation
at Various Air Gaps, With AGC
1000
1000
600
0.50 mm
1.00 mm
1.50 mm
2.00 mm
400
200
0
-200
-400
-600
400
200
0
-200
-400
-600
-800
-1000
-1000
3
6
9
12
15
18
21
24
Target Rotation (°)
0.50 mm
1.00 mm
1.50 mm
2.00 mm
600
-800
0
AG:
0.25 mm
800
AG:
0.25 mm
Differential Signal, VPROC (mV)
Differential Signal, VPROC (mV)
800
0
3
6
9
12
15
18
21
24
Target Rotation (°)
Figure 7. Effect of AGC. The left panel shows the process signal, VPROC, without AGC. The right panel shows the effect with
AGC. The result is a normalized VPROC, which allows optimal performance by the rest of the circuits that reference this signal.
Offset Adjustment
In addition to normalizing performance over varying AG, the
gain control circuitry also reduces the effect of chip, magnet,
and installation offsets. This is accomplished using two DACs
(D to A converters) that capture the peaks and valleys of the
processed signal, VPROC, and use it as a reference for the Threshold Comparator subcircuit, which controls device switching. If
induced offsets bias the absolute signal up or down, AGC and
the dynamic DAC behavior work to normalize and reduce the
impact of the offset on sensor performance.
13
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
SWITCHPOINTS
Switchpoints in the ATS625 are a percentage of the amplitude of
the signal, VPROC, after normalization with AGC. In operation,
the actual switching levels are determined dynamically. Two
DACs track the peaks of VPROC (see the Update subsection).
The switching thresholds are established at 40% and 60% of the
values held in the two DACs. The proximity of the thresholds
near the 50% level ensures the most accurate and consistent
switching, because it is where the slope of VPROC is steepest and
least affected by air gap variation.
ing from the previous two edges. Because variations are tracked
in real time, the sensor has high immunity to target run-out and
retains excellent accuracy and functionality in the presence of
both run-out and transient mechanical events. Figure 9 shows
how the sensor uses historical data to provide the switching
threshold for a given edge.
Dynamic BOP Threshold Determination
The low hysteresis, 20%, provides high performance over various air gaps and immunity to false switching on noise, vibration,
backlash, or other transient events.
UPDATE
The ATS625 incorporates an algorithm that continuously monitors the system and updates the switching thresholds accordingly.
The switchpoint for each edge is determined by the signal result-
VPROC (%)
100
60
BOP
0
Device
State
Figure 8 graphically demonstrates the establishment of the
switching threshold levels.Because the thresholds are established
dynamically as a percentage of the peak-to-peak signal, the
effect of a baseline shift is minimized. As a result, the effects of
offsets induced by tilted or off-center installation are minimized.
V+
On
Off
(A)
Switching Threshold Levels
Dynamic BRP Threshold Determination
At Constant VPROC Level
V+
V+
100
60
BOP
40
BRP
VPROC (%)
VPROC (%)
100
0
Off
On
Off
On
Device
State
Device
State
0
BRP
40
Off
On
(B)
Figure 8. Switchpoint Relationship to Thresholds.The device switches
when VPROC passes a threshold level, BOP or BRP , while changing in the
corresponding direction: increasing for a BOP switchpoint, and decreasing
for a BRP switchpoint.
Figure 9. Switchpoint Determination. The two previous VPROC peaks are
used to determine the next threshold level: panel A, operate point, and
panel B, release point.
14
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Sensor and Target Evaluation
A single curve can be derived from this map data, and be used to
describe the peak-to-peak magnetic field strength versus the size
of the air gap, AG. This allows determination of the minimum
amount of magnetic flux density that guarantees operation of the
sensor, BIN, so the system designer can determine the maximum
allowable AG for the sensor and target system. Referring to figure 11, a BIN of 60 G corresponds to a maximum AG of approximately 2.5 mm.
Magnetic Profile
In order to establish the proper operating specification for a
particular sensor and target system, a systematic evaluation of
the magnetic circuit should be performed. The first step is the
generation of a magnetic map of the target. By using a calibrated
device, a magnetic profile of the system is made. Figure 10 is a
magnetic map of the 60+2 reference target.
Magnetic Map, Reference Target 60+2 with ATS625
300
250
Differential Flux Density, BIN (G)
200
AG
(mm)
150
100
0.75
50
1.00
0
1.50
-50
-100
2.00
-150
2.50
-200
3.00
-250
-300
-350
-400
0
30
60
90
120
150
180
Target Rotation (°)
Peak-Peak Differential Flux Density, BIN (G)
Air Gap Versus Magnetic Field, Reference Target 60+2 with ATS625
800
700
600
500
400
300
200
100
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
AG (mm)
Figure 10. Magnetic Data for the Reference Target 60+2 with ATS625. In the top panel, the Signature Region appears in the center of the plot.
15
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
ACCURACY
While the update algorithm will allow the sensor to adapt to
typical air gap variations, major changes in air gap can adversely
affect switching performance. When characterizing sensor
performance over a significant air gap range, be sure to re-power
the device at each test at different air gaps. This ensures that
self-calibration occurs for each installation condition. See the
Operating Characteristics table and the charts in the Characteristic Data: Relative Timing Accuracy section for performance
information.
REPEATABILITY
Repeatability measurement methodology has been formulated to
minimize the effect of test system jitter on device measurements.
By triggering the measurement instrument, such as an oscillo-
scope, close to the desired output edge, the speed variations that
occur within a single revolution of the target are effectively nullified. Because the trigger event occurs a very short time before
the measured event, little opportunity is given for measurement
system jitter to impact the time-based measurements.
After the data is taken on the oscilloscope, statistical analysis
of the distribution is made to quantify variability and capability. Although complete repeatability results can be found in the
Characteristic Data: Repeatability section, figure 11 shows the
correlation between magnetic signal strength and repeatability.
Because an direct relationship exists between magnetic signal
strength and repeatability, optimum repeatability performance
can be attained through minimizing the operating air gap and
optimizing the target design.
Target Mechanical Profile
Oscilloscope triggers at
n events after low-resolution pulse
Low Resolution Encoder
Next high-resolution encoder pulse
(at target edge)
High Resolution Encoder
Sensor Output
Electrical Profile
(target movement
from pin 1 to pin 4)
Oscilloscope trace
of 1000 sweeps for
the same output edge
Statistical distribution
of 1000 sweeps
X
Figure 11. Repeatability Measurement Methodology
16
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Power Derating
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions*
Minimum-K PCB (single layer, single-sided, with copper limited to
solder pads)
Low-K PCB (single-layer, single-sided with copper limited to
solder pads and 3.57 in.2 (23.03 cm2) of copper area each side)
RθJA
Package Thermal Resistance
Value Units
126
ºC/W
84
ºC/W
*Additional information is available on the Allegro Web site.
Power Derating Curve
TJ(max) = 165ºC
30
VCC(max)
Maximum Allowable VCC (V)
25
20
Low-K PCB
(RQJA = 84 ºC/W)
15
Minimum-K PCB
(RQJA = 126 ºC/W)
10
5
VCC(min)
0
20
40
60
80
100
120
140
160
180
Power Dissipation, PD (m W)
Power Dissipation Versus Ambient
for Sample PCBs
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
Lo
(R w-
K
θJ
A = PC
Mi
n
84 B
(R imu
ºC
mθJ
A =
KP
/W
12
)
6 º CB
C/
W)
20
40
60
80
100
120
140
Temperature, TA (°C)
160
180
17
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating TJ. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, RθJA, is a figure of merit summarizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, RθJC, is
relatively small component of RθJA. Ambient air temperature,
TA, and air motion are significant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD.
PD = VIN × IIN
(1)
ΔT = PD × RθJA
(2)
TJ = TA + ΔT
(3)
Example: Reliability for VCC at TA = 150°C, package SG, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RθJA = 126°C/W, TJ(max) = 165°C, VCC(max) = 26.5 V, and
ICC(max) = 8 mA. Note that ICC(max) at TA = 150°C is lower than
the ICC(max) at TA = 25°C given in the Operating Characteristics
table.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = ΔTmax ÷ RθJA = 15°C ÷ 126 °C/W = 119 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 119 mW ÷ 8 mA = 14.9 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced
RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
For example, given common conditions such as: TA= 25°C,
VIN = 12 V, IIN = 4 mA, and RθJA = 140 °C/W, then:
PD = VIN × IIN = 12 V × 4 mA = 48 mW
ΔT = PD × RθJA = 48 mW × 140 °C/W = 7°C
TJ = TA + ΔT = 25°C + 7°C = 32°C
A worst-case estimate, PD(max), represents the maximum allowable power level, without exceeding TJ(max), at a selected RθJA
and TA.
18
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS625LSG
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
Sensor Evaluation: EMC
Characterization Only
Test Name*
Reference Specification
ESD – Human Body Model
AEC-Q100-002
ESD – Machine Model
AEC-Q100-003
Conducted Transients
ISO 7637-1
Direct RF Injection
ISO 11452-7
Bulk Current Injection
ISO 11452-4
TEM Cell
ISO 11452-3
*Please contact Allegro MicroSystems for EMC performance
19
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
ATS625LSG
Package SG, 4-Pin SIP
5.5 .217
C
E
8.0
5.8
B
1.10 .0433
.315
.228
2.9
4.7
1.10 .0433
.185
.114
E
A
1.7
0.38 .015
.067
1
2
3
4
1.08 .043
0.4 .016
20.95 .825
15.3 .602
A
D
0.6 .024
1.27 .050
Preliminary dimensions, for reference only
Untoleranced dimensions are nominal.
Dimensions in millimeters
U.S. Customary dimensions (in.) in brackets, for reference only
Dimensions exclusive of mold flash, burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Dambar removal protrusion (16X)
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
C Active Area Depth, 0.43 [.017]
D Thermoplastic Molded Lead Bar for alignment during shipment
E Hall elements (2X)
20
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS625LSG
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor
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 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 infringement of patents or other rights of third parties
which may result from its use.
Copyright © 2005, 2006 Allegro MicroSystems, Inc.
21
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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