Allegro ATS673 Self-calibrating tpos gear tooth sensor optimized for automotive cam sensing application Datasheet

ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for
Automotive Cam Sensing Applications
Features and Benefits
Description
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Recognizing the increasingly stringent requirements for EMC/
EMI in automotive applications, Allegro has taken the necessary
steps to design devices that are capable of withstanding the
effects of radiated and conducted transients. The ATS673
and ATS674 devices have been designed specifically for this
purpose. Advanced circuitry on the die allows them to survive
positive and negative transient pulses on both the input and
output.
Tight timing accuracy over operating temperature range
True zero-speed operation
TPOS (True Power-On State)
Air-gap-independent switchpoints
High immunity to vibration
Large operating air gaps
Operation with supply voltages down to 3.3 V
Digital output representing target profile
Single-chip solution for high reliability
Optimized Hall IC/magnet system
The ATS673 and ATS674 devices retain all of the same
characteristics as the ATS671 and ATS672. The devices remain
true zero-speed gear tooth sensors with optimized Hall IC/
magnet configuration in an SIP (single in-line package). The
SIP assembly consists of a molded package that holds together
a samarium cobalt magnet, a pole piece, and a true zero-speed
Hall IC that has been optimized to the magnetic circuit.
Continued on the next page…
Packages: 4 pin SIP (suffix SE)
The sensor incorporates a single element Hall IC that switches
in response to magnetic signals created by a ferrous target.
The IC contains a sophisticated digital circuit designed
to eliminate the detrimental effects of magnet and system
offsets. Signal processing is used to provide zero-speed
Continued on the next page…
Not to scale
Functional Block Diagram
V+
VCC
Voltage
Regulator
(Analog)
Voltage
Regulator
(Digital)
VREG(A)
Hall
Amp
VREG(D)
Automatic
Gain
Control
Offset Adjust
Temperature
Coefficient
Adjust
Offset
LPF
TC
VPROC
VREF
9-Bit
PDAC
9
Comp_P
Clock
Continuous
Update Logic
0.1 μF
CBYPASS
9-Bit
Counter
Threshold
Output
Output State
Clock
Continuous
Update Logic
Comp_N
Output State
9-Bit
Counter
9
9-Bit
NDAC
TPOS
VREG(A)
VREG(D)
Power-On
Reset
Output
Driver
Threshold
Comparator
TPOS Trim
GND
TEST
(Recommended)
ATS673-DS, Rev. 1
VOUT
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Features and Benefits (continued)
▪ AGC and reference adjust circuit
▪ Undervoltage lockout
Description (continued)
performance independent of air gap and also to dynamically adapt
device performance to the typical operating conditions found in
automotive applications, particularly cam sensing applications
(reduced vibration sensitivity).
High-resolution (9-bit) peak detecting DACs are used to set the
adaptive switching thresholds of the devices, ensuring high accuracy
even in the presence of gear eccentricity. Hysteresis in the thresholds
reduces the negative effects of anomalies in the magnetic signal
(such as magnetic overshoot) associated with the targets used in
many automotive applications. The ATS673 and 674 also include
a low bandwidth filter that increases the noise immunity and the
signal to noise ratio of the sensor.
Two options are available for output polarity, low over tooth (LT)
and high over tooth (HT). For applications requiring absolute
accuracy use the ATS674. The ATS673 should be used for targets
with high wobble.
Selection Guide
Part Number
Pb-free1
ATS673LSETN-LT-T
Yes
Low
ATS673LSETN-HT-T
Yes
High
ATS674LSETN-LT-T
Yes
Low
ATS674LSETN-HT-T
Yes
High
VOUT (Over Tooth)
Packing2
Application
High target wobble
13-in. reel, 450 pieces/reel
High absolute edge detection accuracy
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: ATS673LSETN-LT, ATS673LSETN-HT, ATS674LSETN-LT, and ATS674LSETN-HT.
2Contact Allegro for additional packing options.
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
Supply Voltage
VCC
28
V
Reverse-Supply Voltage
VRCC
–18
V
Continuous Output Current
IOUT
20
mA
Reverse Output Current
IROUT
50
mA
–40 to 150
ºC
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Pin-out Diagram
Range L
Terminal List
Name
VCC
1 2
3 4
Description
Number
Connects power supply to chip
1
VOUT
Device output
2
TEST
For Allegro use, float or tie to GND
3
GND
Ground terminal
4
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
OPERATING CHARACTERISTICS Valid at TA = –40°C to 150°C, TJ ≤ TJ(max), over full range of AG, unless otherwise noted
Characteristic
Min.
Typ.1
Max.
Units
Operating; TJ < TJ(Max)
3.3
–
26.5
V
Symbol
Test Conditions
ELECTRICAL CHARACTERISTICS
Supply Voltage
VCC
–
–
<VCC(Min)
V
Supply Zener Clamp Voltage
VZSupply
ICC = ICC(Max) + 3 mA, TA = 25°C
28
31
35
V
Supply Zener Current2
IZSupply
Undervoltage Lockout
VCCUV
VSupply = 27 V
–
–
14
mA
Supply Current
ICC
Output = OFF or ON
3
6.5
11
mA
Reverse Supply Current
IRCC
VRCC = –18 V
–
–5
–10
mA
tPO
Gear Speed < 100 rpm; VCC > VCC(Min)
–
–
500
μs
ISINK = 15 mA, Output = ON
–
200
450
mV
POWER-ON CHARACTERISTICS
Power-On Time3
OUTPUT CHARACTERISTICS
Low Output Voltage
VOUT(Sat)
Output Zener Voltage
VZOUT
IOUT = 3 mA, TA = 25°C
30
–
–
V
Output Current Limit
IOUTLIM
Output = ON, VOUT = 12 V
35
57
90
mA
Output Leakage Current
IOUTOFF
Output = OFF, VOUT = VCC(Max)
–
–
10
μA
Output Rise Time
tr
10/90% points; RLOAD = 500 Ω, CLOAD = 10 pF, TA = 25°C
–
0.9
5
μs
Output Fall Time
tf
10/90% points; RLOAD = 500 Ω, CLOAD = 10 pF, TA = 25°C
Over tooth
HT device option
Over valley
–
–
0.5
HIGH
5
–
μs
V
V
Output Polarity
VOUT
LT device option
–
LOW
–
Over tooth
–
LOW
–
V
Over valley
–
HIGH
–
V
Continued on the next page...
V+
Output Rise and Fall Time
VOUT(High)
%
100
90
10
0
VOUT(Low)
t+
tr
tf
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS, continued Valid at TA = –40°C to 150°C, TJ ≤TJ(max), over full range of AG, unless otherwise noted
Characteristic
Symbol
Test Conditions
Min.
Typ.1
Max.
Units
SWITCHPOINT CHARACTERISTICS
Tooth Speed
Tooth frequency, target generating sinusoidal signal
0
–
8
kHz
BW
Corresponds to output switching frequency – 3 dB
–
40
–
kHz
Operate
BOP
ATS673 % of peak-to-peak, referenced to tooth signal,
ATS674 AG < AG(Max)
–
40
–
%
–
30
–
%
Release
BRP
ATS673 % of peak-to-peak, referenced to tooth signal,
ATS674 AG < AG(Max)
–
50
–
%
–
40
–
%
Quantity of rising edges required to complete edge detection calibration
–
–
3
edges
Bandwidth
S
CALIBRATION CHARACTERISTICS4
Initial Calibration
CalIC
AGC Disable
CalAGC
Quantity of rising edges required to complete Automatic
Gain Control calibration
–
–
3
edges
Calibration Update
CalUPD
Quantity of rising edges required to update edge detection
calibration while running after initial calibration
–
Continuous
–
edges
PERFORMANCE CHARACTERISTICS3
TPOS Air Gap Range5
Operational Air Gap Range
AGTPOS
AG
TPOS functionality guaranteed
0.5
–
2.5
mm
TPOS guaranteed, output switching, running mode
0.5
–
2.5
mm
Extended Minimum Air Gap6
AGEXTMIN
Output switching, running mode; valleys may be detected
as teeth in this range
–
–
0.5
mm
Extended Maximum Air Gap7
AGEXTMAX
Output switching, running mode; teeth may be detected as
valleys in this range
2.5
–
5
mm
–
3
6
deg
–
3
6
deg
Relative Timing Accuracy4,8
Phase Delay9
1Typical
ErrICREL
ATS673 During initial calibration; rising or falling edges,
gear speed = 1000 rpm, target eccentricity
ATS674 < 0.1 mm
ErrRELR
ATS673 Rising edges; after initial calibration, gear speed
ATS674 = 1000 rpm, target eccentricity < 0.1 mm
–
0.5
0.8
deg
–
0.4
0.8
deg
ErrRELF
ATS673 Falling edges; after initial calibration, gear speed
ATS674 = 1000 rpm, target eccentricity < 0.1 mm
–
0.8
1.2
deg
–
0.6
1.2
deg
After initial calibration, AG = 1.5 mm, TA = 25°C
–
1.6 x 10–4
–
deg/rpm
ΔErrSREL
values are taken at VCC = 12 V and TA =
2I
ZSupply(Max) is equivalent to ICCON(Max) + 3 mA.
3Using reference target 8X.
25°C.
4The
term edge refers to a mechanical edge, such as the side of a gear tooth, passing under the device. Rising edge: from valley to approaching tooth.
Falling edge: from tooth to approaching valley.
5The TPOS Air Gap Range is the range of installation air gaps within which the TPOS (True Power-On State) function is guaranteed to correctly detect
a tooth when powered-on over a tooth and correctly detecting a valley when powered-on over a valley, using reference target 8X or equivalent, as
specified in the Target/Gear Parameters for Correct TPOS Operation section in this document.
6The Extended Minimum Air Gap is a range of installation air gaps, smaller than AG
(Min), within which the the device will accurately detect target features but TPOS is NOT guaranteed to be fully accurate, possibly evaluating the initial valley as a tooth.
7The Extended Maximum Air Gap is an extended range of installation air gaps, greater than AG
(Max), within which the the device will accurately detect
target features but TPOS is not guaranteed to be fully accurate, possibly evaluating the intiial tooth as a valley.
8Relative Timing Accuracy is the change in edge position before the resulting change in device output; for a single device, over the full Operational Air
Gap Range, AG, and Operating Ambient Temperature, TA , range.
9Phase Delay is the change in edge position at detection, through the full operational Tooth Speed, S, range for a single device, and at a single ambient temperature, TA, and installation air gap, AG.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Air Gap Comparisons
Target (Gear)
Extended Maximum Air Gap, AGEXTMAX
Installation Air Gap
9
Operational Air Gap Range, AG
TPOS Air Gap Range, AGTPOS
Extended Minimum Air Gap Air Gap, AGEXTMIN
Sensor Device
Branded Face
Relative Timing Accuracy
Target
Mechanical Profile
V+
Sensor Output
Electrical Profile
-HT Option
VOUT
t
ErrRELR(Max – Min)
ErrRELF(Max – Min)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Reference Target (Gear) Information
REFERENCE TARGET 8X
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
23.6
mm
Circular Valley Length
tv
Length of valley, with respect
to sensor; measured at Do
23.6
mm
Tooth Whole Depth
ht
5
mm
–
–
Outside Diameter
Material
CRS 1018
Symbol Key
Branded Face
of Sensor
tV
t
Characteristic
ØDO
F
ht
Air Gap
Branded Face
of Sensor
Reference Target 8X
Figure 1. Configuration with Reference Target
Target/Gear Parameters for Correct TPOS Operation
For TPOS to function as specified, the target must generate a
minimum of 120 G difference between the magnetic field over
a tooth and the field over a valley, at the maximum installation
air gap. A target complying with the material and dimensions
cited for the reference target 8X, generates the required 120 G
differential.
The following recommendations should be followed in the
design and specification of targets:
• Tooth width, t ≥ 5 mm
• Valley width, tv > 13 mm
• Valley depth, ht > 5 mm
• Tooth thickness, F ≥ 5 mm
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Characteristic Data: Electrical
Supply Current (On) Versus Ambient Temperature
Supply Current (Off) Versus Ambient Temperature
11
10
10
ICC(ON) (mA)
9
VCC (V)
8
26.5
15.0
3.3
7
6
ICC(OFF) (mA)
11
9
VCC (V)
26.5
15.0
3.3
8
7
6
5
5
4
4
3
3
-50
-25
0
25
50
75
100
125
150
175
-50
-25
0
25
Supply Current (On) Versus Supply Voltage
100
125
150
175
Supply Current (Off) Versus Supply Voltage
11
11
10
10
9
9
TA (°C)
8
-40
0
25
85
150
7
6
5
ICC(OFF) (mA)
ICC(ON) (mA)
75
TA (°C)
TA (°C)
TA (°C)
8
-40
0
25
85
150
7
6
5
4
4
3
3
0
5
10
15
20
25
30
0
5
10
Output Voltage (Low) Versus Ambient Temperature
20
25
30
Output Leakage Current (Off) Versus Ambient Temperature
500
10
400
200
100
IOUT(OFF) (uA)
8
IOUT (mA)
20
15
10
300
6
4
2
0
-50
15
VCC (V)
VCC (V)
VOUT(SAT) (mV)
50
0
-25
0
25
50
75
TA (°C)
100
125
150
175
-50
-25
0
25
50
75
100
125
150
175
TA (°C)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
7
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Characteristic Data: Relative Timing Accuracy
ATS673 Relative Timing Accuracy Versus Air Gap
ATS673 Relative Timing Accuracy Versus Air Gap
Rising Mechanical Edge
Falling Mechanical Edge
1000 rpm, Relative to 0.5 mm Air Gap
1000 rpm, Relative to 0.5 mm Air Gap
1.2
0.0
1.0
-0.2
TA (°C)
-0.3
–40
0
25
85
150
-0.4
-0.5
-0.6
Edge Position (°)
Edge Position (°)
-0.1
-0.7
-0.8
TA (°C)
0.8
–40
0
25
85
150
0.6
0.4
0.2
0.0
0.5
1.0
1.5
2.0
2.5
0.5
3.0
1.0
AG (mm)
2.0
2.5
3.0
AG (mm)
ATS674 Relative Timing Accuracy Versus Air Gap
ATS674 Relative Timing Accuracy Versus Air Gap
Rising Mechanical Edge
Falling Mechanical Edge
1000 rpm, Relative to 0.5 mm Air Gap
1000 rpm, Relative to 0.5 mm Air Gap
0.0
1.2
-0.1
1.0
-0.2
TA (°C)
-0.3
–40
0
25
85
150
-0.4
-0.5
-0.6
Edge Position (°)
Edge Position (°)
1.5
TA (°C)
0.8
–40
0
25
85
150
0.6
0.4
0.2
-0.7
-0.8
0.0
0.5
1.0
1.5
2.0
2.5
0.5
3.0
1.0
AG (mm)
2.0
2.5
3.0
AG (mm)
Relative Timing Accuracy Versus Air Gap
Relative Timing Accuracy Versus Air Gap
Rising Mechanical Edge
Falling Mechanical Edge
1.5 mm Air Gap, Relative to 0.5 mm Air Gap
1.5 mm Air Gap, Relative to 0.5 mm Air Gap
0.40
0.40
0.30
0.30
0.20
0.10
ATS673
ATS674
0
-0.10
-0.20
-0.30
Edge Position (°)
Edge Position (°)
1.5
0.20
0.10
ATS673
ATS674
0
-0.10
-0.20
-0.30
-0.40
-0.40
0
500
1000
1500
Gear Speed (rpm)
2000
2500
0
500
1000
1500
2000
2500
Gear Speed (rpm)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Operational Description
is illustrated in figure 2. The difference in the magnetic gradients
created by teeth and valleys allows the devices to generate a
digital output signal.
Assembly Description
The ATS673 and ATS674 true zero-speed gear tooth sensors
have a 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.
Output
After proper power is applied to the devices, they are then
capable of providing digital information that is representative of
the profile of a rotating gear, as illustrated in figure 3. 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 Hall effect sensor IC, a 4-pin leadframe and a specially designed rare-earth
magnet. The Hall IC supports a Hall element that measures the
magnetic gradient created by the passing of a ferrous object. This
Target (Gear)
Low-B field
Hall element
Leadframe
High-B field
Hall IC
North Pole
Sensor Device
Back-Biasing magnet
Plastic
Pole piece
(Concentrator)
South Pole
(A)
(B)
Figure 2. Device Cross Section. Motion of the target is detected by the Hall element mounted on the Hall IC. Panel A, the presence of a tooth feature on
the target is distinguished by a high magnetic flux density, B. Panel B, the presence of a valley feature is distinguished by its low magnetic flux density.
Target
Mechanical Profile
Target
Magnetic Profile
-LT Option
Sensor Output
Switch State
Sensor Output
Electrical Profile
-HT Option
Sensor Output
Switch State
Sensor Output
Electrical Profile
B
BIN
0
On
Off
On
Off
On
Off
On
Off
Off On
Off
On
Off
On
Off
On
V+
VOUT
V+
VOUT
Figure 3. 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, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
9
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Power Supply Protection
The ATS673 and ATS674 contain 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.
TPOS (True Power-On State) Operation
Under specified operating conditions, the devices are guaranteed to attain a specified output voltage polarity at power-on, in
relation to the target feature nearest the device at that time. Both
devices offer the options of either high or low polarity over initial tooth or valley. This polarity also applies throughout device
operation.
Start-Up Detection
These devices provide an output polarity transition at the first
mechanical edge after power-on.
Internal Electronics
These devices contain a self-calibrating Hall effect IC that
provides a Hall element, 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.
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.
VS
1
VCC
CBYPASS
0.1 μF 3
RPU
ATS673/674
TEST
VOUT
2
Sensor Output
GND
4
Figure 5. Power Supply Protection Typical Circuit
10
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
adjusted, keeping the internal signal amplitude constant over the
air gap range of the device. This feature ensures that operational
characteristics are isolated from the effects of changes in AG.
The effect of AGC is shown in figure 7.
AGC (Automatic Gain Control)
The AGC feature is implemented by a unique patented selfcalibrating circuitry. After each power-on, the devices measure
the peak-to-peak magnetic signal. The gain of the sensor is then
Magnetic Flux Density Versus Target Edge Position
600
AG (mm):
Flux Density, B (G)
500
1.50
2.00
400
2.50
300
3.00
3.50
200
100
0
0
10
20
30
40
50
60
70
80
90
Target Rotation (°)
Internal Analog Signal after AGC Versus Target Edge Position
2.0
AG (mm):
1.50
2.00
2.50
3.00
3.50
VPROC (V)
1.5
1.0
0.5
0
0
10
20
30
40
50
60
70
80
90
Target Rotation (°)
Figure 7. Effect of AGC. The upper panel shows the magnetic gradient detected at the Hall element, with no amplification.
The lower panel displays the corresponding internal processed signal, VPROC. This normalized electrical signal allows optimal
performance by the rest of the circuits that reference this signal.
11
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Switchpoints
Switchpoints in the ATS673 and ATS674 are established dynamically as a percentage of the amplitude of the signal, VPROC, after
normalization with AGC. Two DACs track the peaks of VPROC
(see the Update subsection).
The switching thresholds are established at fixed percentages
of the values held in the two DACs. The value of the thresholds
has been carefully selected, where the signal is steepest and least
affected by air gap variation, thus providing the most accurate
and consistent switching.
The low hysteresis, 10%, provides high performance over various air gaps while maintaining immunity to false switching on
noise, vibration, backlash, or other transient events.
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.
Target
Mechanical
Profile
V+
100
BRP%
BOP%
VPROC (%)
ATS673 and
ATS674
0
Device
State
-LT option
-HT option
On
Off
On
Off
Off
On
Off
On
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.
12
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Update
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 devices use historical data to provide the switching
thresholds for a given edge.
The ATS673 and ATS674 incorporate an algorithm that continuously monitors the system and updates the switching thresholds
accordingly. The switchpoint for each transition is determined
by the previous two transitions. Because variations are tracked
(A) TEAG varying; cases such as
eccentric mount, out-of-round region,
normal operation position shift
(B) Internal analog signal, VPROC,
typically resulting in the sensor
V+
Smaller
TEAG
Smaller
TEAG
Target
Sensor
VPROC (V)
Larger
TEAG
Target
Smaller
TEAG
Hysteresis Band
(Delimited by switchpoints)
Larger
TEAG
Sensor
360
0
Target Rotation (°)
(C) Referencing the internal analog signal, VPROC, to continuously update device response
Determinant
Peak Values
BOP1
BRP1
Pk1, Pk2
Pk2, Pk3
BOP2
BRP2
Pk3, Pk4
Pk4, Pk5
BOP3
BRP3
Pk5, Pk6
Pk6, Pk7
BOP4
Pk7, Pk8
BRP4
Pk8, Pk9
V+
BHYS
Pk1
BHYS
BHYS
Pk9
BHYS
Pk7
Pk3
Pk5
VPROC (V
Switchpoint
BOP1
BOP2
BOP3
BRP1
BOP4
BRP3
BRP4
BRP2
Pk4
Pk6
Pk2
Pk8
BHYS
BHYS
BHYS
BHYS
t+
Figure 9. The Continuous Update algorithm allows the Allegro sensor to immediately interpret and adapt to significant variances in the magnetic field
generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and
similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently
update the device switchpoints (BOP and BRP). The hysteresis, BHYS(#x), at each target feature configuration results from this recalibration, ensuring that
it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC.
As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the sensor as a varying magnetic field, which
results in proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish accurate
switchpoints based on the fluctuation of VPROC, as shown in panel C.
13
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Sensor and Target Evaluation
Magnetic Profile
In order to establish the proper operating specification for a particular sensor device 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 8X reference target.
A pair of curves can be derived from this map data, and be used
to describe the tooth and valley magnetic field strength, B, 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, so the system designer can determine the maximum
allowable AG for the sensor and target system. One can also
determine the TPOS air gap capabilities of the sensor by comparing the minimum tooth signal to the maximum valley signal.
Magnetic Map, Reference Target 8X with SE Package
1600
1400
Flux Density, B (G)
1200
1000
800
600
400
200
0
0
60
120
180
240
300
360
Target Rotation (°)
Air Gap Versus Magnetic Field, Reference Target 8X with SE Package
1300
1200
1100
Flux Density, B (G)
1000
900
800
700
600
500
Tooth
400
Valley
300
200
100
0
0
1.0
2.0
3.0
4.0
5.0
6.0
AG (mm)
Figure 10. Magnetic Data for the 8X Reference Target and SE package.
14
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Accuracy
While the update algorithm will allow the sensor devices 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
repower 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.
Sensor Evaluation: EMC
Characterization Only
Test Name*
Reference Specification
ESD – Human Body Model
ESD – Machine Model
Conducted Transients
Direct RF Injection
Bulk Current Injection
TEM Cell
*Please contact Allegro for EMC performance
AEC-Q100-002
AEC-Q100-003
ISO 7637-1
ISO 11452-7
ISO 11452-4
ISO 11452-3
Related Documents
Documents that can be found on the Allegros web site,:
www.allegromicro.com:
• Definition of Terms (Pub 26004)
• Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating,
and Lead forming (AN27703.1)
• Storage of Semiconductor Devices (Pub 26011)
• Hall Effect Applications Guide (Pub 27701)
• Applications Note: Back-Biased Packaging Advances (SE, SG
& SH versus SA & SB)
15
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
Power Derating
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions*
RθJA
Package Thermal Resistance
Value Units
1-layer PCB with copper limited to solder pads
101
ºC/W
1-layer PCB with copper limited to solder pads and 3.57 in.2
(23.03 cm2) of copper area each side
77
ºC/W
*Additional information is available on the Allegro Web site.
Power Derating Curve
30
VCC(max)
Maximum Allowable VCC (V)
25
20
1-Layer PCB
(RθJA = 77 ºC/W)
15
Pads Only PCB
(RθJA = 101 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
L
(R owK
θJ
A = PC
77 B
ºC
/W
Mi
(R nim
um
θJ
A =
10 K P
1 º CB
C/
W
)
20
40
60
)
80
100
120
140
Temperature, TA (°C)
160
180
16
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
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 SE, using
minimum-K PCB.
Observe the worst-case ratings for the device, specifically:
RθJA = 101°C/W, TJ(max) = 165°C, VCC(max) = 26.5 V, and
ICC(max) = 11 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 ÷ 101 °C/W = 91 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 91 mW ÷ 11 mA = 8.3 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.
17
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
ATS673 and
ATS674
Package SE, 4-Pin SIP
7 .276
10
C
.394
B
3.3 .130
E
6.2 .244
4.9
.193
1.3
0.38 .015
A
.051
1.08 .043
20.95 .825
11.6 .457
1
2
3
4
A
D
0.6 .240
1.27
.050
2 .079
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 mm [.017]
D Thermoplastic Molded Lead Bar for alignment during shipment
E Hall element (not to scale)
18
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ATS673 and
ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized
for Automotive Cam Sensing Applications
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; 6,297,627; 6,525,531; 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.
19
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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