ATS625LSG: True Zero-Speed Low-Jitter High Accuracy Gear Tooth Sensor IC

ATS625LSG
True Zero-Speed Low-Jitter
High Accuracy Gear Tooth Sensor IC
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: October 31, 2011
Recommended Substitutions:
For existing customer transition, and for new customers or new applications, refer to the ATS627LSGTN-T.
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.
ATS625LSG
True Zero-Speed Low-Jitter
High Accuracy Gear Tooth Sensor IC
Features and Benefits
Description
▪
▪
▪
▪
▪
▪
▪
▪
▪
▪
The ATS625 true zero-speed gear tooth sensor IC is an optimized
Hall IC and rare earth pellet configuration that provides a
manufacturer-friendly solution for digital gear tooth sensing
applications. The over-molded package holds together a
samarium cobalt pellet, 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 device 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 device is optimized for
crank applications that utilize targets that possess signature
regions.
Continued on the next page…
Package: 4 pin SIP (suffix SG)
The ATS625 is provided in a 4-pin SIP. It is lead (Pb) free,
with 100% matte tin plated leadframe.
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
Reference
Generator
NDAC
NPeak
Threshold
Logic
NThresh
Current
Limit
GND
AUX
(Recommended)
ATS625LSG-DS, Rev. 5
Output
Transistor
VOUT
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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-T2
Packing1
Tape and Reel 13-in. 800 pcs./reel
1Contact Allegro
2Some
for additional packing options.
restrictions may apply to certain types of sales. Contact Allegro for details.
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
26.5
V
Supply Voltage
VCC
Reverse-Supply Voltage
VRCC
–18
V
Reverse-Supply Current
IRCC
50
mA
Reverse-Output Voltage
VROUT
–0.5
V
IOUT
10
mA
Output Sink Current
See Power Derating section
Operating Ambient Temperature
TA
–40 to 150
ºC
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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
60
90
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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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 package 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 Device 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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Reference Target (Gear) Information
REFERENCE TARGET 60+2
Symbol
Test Conditions
Typ.
Unit
120
mm
Do
Outside diameter of target
Face Width
F
Breadth of tooth, with respect to
branded face
6
mm
Circular Tooth Length
t
Length of tooth, with respect to
branded face; measured at Do
3
mm
tSIG
Length of signature tooth, with
respect to branded face; measured at Do
15
mm
Circular Valley Length
tv
Length of valley, with respect to
branded face; measured at Do
3
mm
Tooth Whole Depth
ht
3
mm
–
–
Signature Region Circular Tooth Length
Material
Low Carbon Steel
Branded Face
of Package
t,t
S
Outside Diameter
Symbol Key
IG
Characteristics
tV
ØDO
F
ht
Air Gap
Signature Region
Pin 4
Pin 1
Branded Face
of Package
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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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)
50
75
100
125
150
175
VOUT(SAT) Versus TA
10
400
8
350
6
VOUT (V)
2
26.5
20.0
12.0
4.0
0
-2
-4
Voltage (mV)
300
4
IOUT (mA)
25
20
15
10
5
250
200
150
100
-6
50
-8
0
-10
-50
25
Temperature (°C)
IOUT(OFF) Versus TA
Current (uA)
VCC (V)
-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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Characteristic Data: Relative Timing Accuracy
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient Temperature
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 Temperature
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
Target Speed, S (rpm)
50
100
150
Temperature, TA (°C)
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient Temperature
0
500
1000
1500
2000
2500
Rising Edge Following Signature Tooth
0
200
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)
50
100
500
1000
1500
2000
0.5
0.0
-0.5
-1.0
-1.5
-50
0
50
100
150
200
Temperature, TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient Temperature
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 Temperature
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
Target Speed, S (rpm)
50
100
150
Temperature, TA (°C)
Relative Timing Accuracy Versus Speed
Relative Timing Accuracy Versus Ambient Temperature
0
500
1000
1500
2000
2500
Rising Edge Following Signature Tooth
0
200
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)
50
100
500
1000
1500
2000
0.5
0.0
-0.5
-1.0
-1.5
-50
0
50
100
150
200
Temperature, TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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 (°)
0.0
0.5
1.0
1.5
Air Gap (mm)
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
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 (°)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
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
Repeatabilty (°)
Edge Position (°)
TA = –40, 0, 25, 85, 150 (°C)
S = 50, 100, 500, 1000, 1500, 2000 (rpm)
TA (°C)
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
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Device Description
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.
Package Description
The ATS625LSG is a combined Hall IC and rare-earth pellet
configuration that is fully optimized to provide digital detection of gear tooth edges. This device 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 chip 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.
Hall Technology
The ATS625 contains a single-chip differential Hall effect sensor IC, a 4-pin leadframe, a samarium cobalt pellet, and a flat
ferrous pole piece. The Hall IC consists of two Hall elements
spaced 2.2 mm apart, and each independently measures the
Target (Gear)
Element Pitch
Hall Element 2
Dual-Element
Hall Effect Device
Hall Element 1
Hall IC
Pole Piece
(Concentrator)
South Pole
Back-biasing
Rare Earth Pellet
Plastic
North Pole
(Pin n >1 Side)
1
4
(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 package. 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
Branded Face
of Package
Rotating Target
Signature Tooth
B+
BIN
IC Output
Switch State
On
Off
On
Off
On
Off
On
Off
On
Off
On Off On Off On Off
V+
IC Output
Electrical Profile
Target Motion from
Pin 1 to Pin 4
VOUT
IC 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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
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 IC.
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
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.
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.
VS
1
VCC
CBYPASS
0.1 μF
RPU
ATS625
3
AUX
VOUT
2
Output
GND
4
Figure 5. Power Supply Protection Typical Circuit
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
ATS625LSG
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
Device 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 synchronized by the third edge. The
actual behavior is affected by: target rotation direction relative to
Package
Pin 4 Side
the package, target feature (tooth, rising edge, falling edge, or
valley) that is centered on the device at power-on, and fact that
the chip 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 Package
Package
Pin 1 Side
Target Mechanical Profile
Target Magnetic Profile
IC 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)
IC start-up location
Package
Pin 1 Side
Target Motion Relative to Package
Package
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.
IC Output, VOUT
(Start-up over valley)
(Start-up over rising edge)
(Start-up over tooth)
(Start-up over falling edge)
IC 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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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 circuit 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 device performance.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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 device 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 device 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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
IC 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 IC, BIN, so the system designer can determine the maximum
allowable AG for the IC 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 IC 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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Accuracy
While the update algorithm will allow the device to adapt to
typical air gap variations, major changes in air gap can adversely
affect switching performance. When characterizing IC 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 oscilloscope, 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
IC 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
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
16
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
17
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
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, RJA, 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, RJC, is
relatively small component of RJA. 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

Observe the worst-case ratings for the device, specifically:
RJA = 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:
Tmax = 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) = Tmax ÷ RJA = 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
(1)
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤VCC(est).
(3)
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced
RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
T = PD × RJA (2)
TJ = TA + ΔT
Example: Reliability for VCC at TA = 150°C, package SG, using
minimum-K PCB.
For example, given common conditions such as: TA= 25°C,
VIN = 12 V, IIN = 4 mA, and RJA = 140 °C/W, then:
PD = VIN × IIN = 12 V × 4 mA = 48 mW

T = PD × RJA = 48 mW × 140 °C/W = 7°C
TJ = TA + T = 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 RJA
and TA.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
18
ATS625LSG
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
Device 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
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
19
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Package SG, 4-Pin SIP
5.50±0.05
F 1.10
1.10 F
E
B
8.00±0.05
LLLLLLL
NNN
5.80±0.05
E1
E2
YYWW
Branded
Face
1.70±0.10
D
4.70±0.10
1
2
3
4
= Supplier emblem
L = Lot identifier
N = Last three numbers of device part number
Y = Last two digits of year of manufacture
W = Week of manufacture
A
0.60±0.10
Standard Branding Reference View
0.71±0.05
For Reference Only, not for tooling use (reference DWG-9002)
Dimensions in millimeters
A Dambar removal protrusion (16X)
+0.06
0.38 –0.04
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
C Thermoplastic Molded Lead Bar for alignment during shipment
24.65±0.10
D Branding scale and appearance at supplier discretion
0.40±0.10
15.30±0.10
E
Active Area Depth, 0.43 mm
F
Hall elements (E1, E2), not to scale
1.0 REF
A
1.60±0.10
C
1.27±0.10
0.71±0.10
0.71±0.10
5.50±0.10
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
20
True Zero-Speed Low-Jitter High Accuracy
Gear Tooth Sensor IC
ATS625LSG
Revision History
Revision
Revision Date
Rev. 5
June 27, 2011
Description of Revision
Update IOUT
Copyright ©2005-2011, Allegro MicroSystems, Inc.
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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
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.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
21
Similar pages