ATS675 Datasheet

ATS675LSE
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
Features and Benefits
Description
▪ Optimized for automotive camshaft sensing
▪ True target state recognition at device power-on (TPOS)
and at zero target speed
▪ Chopper stabilization reduces offset drift
▪ Digital output polarity option: follow or invert target profile
▪ Rapid calibration and transition to Running mode
▪ Automatic Gain Control (AGC) during calibration
eliminates effects of air gap variations
▪ Tight timing accuracy over full operating
temperature range
▪ Operation at supply voltages as low as 3.3 V
▪ Undervoltage lockout (UVLO)
The ATS675 is a next generation member of the Allegro® True
Power-On State (TPOS) sensor IC family, offering improved
accuracy compared to prior generations, and performing at
absolutely zero target speed. An output polarity option allows
customization for specific applications.
The device incorporates a single Hall-element IC with an
optimized custom magnetic circuit that switches in response to
magnetic signals. The resulting output of the device is a digital
representation of a ferromagnetic target profile.
The IC contains a sophisticated digital circuit designed to
eliminate the detrimental effects of magnetic and system offsets.
Signal processing is used to provide target state recognition
at zero rotational speed, consistent switchpoints regardless
of air gap, and dynamically adapt device performance to the
typical operating conditions found in automotive environments,
particularly cam sensing applications.
Package: 4-pin SIP (suffix SE)
High-resolution peak-detecting DACs are used to set the
adaptive switching thresholds of the device. The ATS675 also
includes a filter that increases the noise immunity and the
signal-to-noise ratio of the IC.
The device is provided in a 4-pin SIP package (SE) that is lead
(Pb) free with 100% matte tin leadframe plating.
Not to scale
Typical Application
VS
VPU
CBYPASS
0.1 μF
RPU
1
VCC
3
A
ATS675
TEST
OUT
GND
4
2
Output
CL
A Recommended
Figure 1. Operational circuit for the ATS675
ATS675LSE-DS, Rev. 2
ATS675LSE
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
Selection Guide
Part Number
Output Protocol
ATS675LSETN-LT-T
Output low opposite target tooth
ATS675LSETN-HT-T
Output high opposite target tooth
*Contact Allegro for additional packing options
Packing*
13-in. reel, 450 pieces per reel
Absolute Maximum Ratings
Characteristic
Symbol
Rating
Unit
28
V
VRCC
–18
V
Reverse Output Voltage
VROUT
–0.5
V
Reverse Supply Current
IRCC
–50
mA
30
mA
–50
mA
Supply Voltage
VCC
Reverse Supply Voltage
Output Current
Reverse Output Current
IOUT(sink)
Notes
Refer to Power Derating curve
Internal current limiting is intended to protect
the device from output short circuits, but is not
intended for continuous operation.
IROUT
Operating Ambient Temperature
TA
–40 to 150
ºC
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Range L
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Functional Block Diagram
VCC
Regulator
(Analog)
Running
Mode
Threshold
Regulator
(Digital)
Baseline
Trim
Oscillator
Hall
Amp
+/–
Low
Pass
Filter
NDAC
Update
Logic
+/–
PDAC
DDA
Multiplexed
Test Signals
TEST
Running
Mode
Threshold
Selector
OUT
Sensitivity TC
Compensation
Automatic
Gain Adjust
TPOS
Trim
Mode
Control
Dynamic
Threshold
DAC
Current
Limit
TPOS
GND
Pin-out Diagram
Terminal List
1 2
3
Number
Name
Function
1
VCC
Supply voltage
2
OUT
Open drain output
3
TEST
Test pin; connection to GND recommended
4
GND
Ground
4
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
ATS675LSE
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS Valid using reference target 8X, TA ,TJ , and VCC within specification, unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.1
Max.
Unit
Electrical Characteristics
Supply Voltage2
Undervoltage Lockout
VCC
Operating, TJ < TJ(max)
3.3
–
24
V
VCCUV
VCC = 0 → 5 V or 5 → 0 V
–
–
3.3
V
Supply Zener Clamp Voltage
VZSUPPLY
ICC = ICC(max) + 3 mA, TA = 25°C
28
33
40
V
Supply Zener Current3
IZSUPPLY
VSUPPLY = 28 V
–
–
13
mA
–
6.5
10
mA
–
–
–10
mA
fc
–
500
–
kHz
VZTEST
–
6
–
V
–
–
1
ms
Supply Current
ICC
Reverse Battery Current4
IRCC
Chopping Frequency
TEST Pin Zener Clamp
Voltage5
VRCC = –18 V
Power-On Characteristics
Power-On Time6
tPO
VCC > VCC(min), fSIG < 200 Hz
Output Stage Characteristics
Output Profile
Polarity7
Output On Voltage
VOUT(SAT)
LT option, measured
as VOUT , device
electrically connected
as in figure 1
Opposite to Tooth
(Output State = On)
–
Low
–
V
Opposite to Valley
(Output State = Off)
–
High
–
V
HT option, measured
as VOUT , device
electrically connected
as in figure 1
Opposite to Tooth
(Output State = Off)
–
High
–
V
Opposite to Valley
(Output State = On)
–
Low
–
V
–
–
400
mV
mV
IOUT = 10 mA, Output State = On
IOUT = 15 mA, Output State = On
–
–
450
Output Zener Voltage
VZOUT
TA = 25°C, IOUT = 3 mA
30
–
–
V
Output Current Limit
IOUTLIM
Output State = On
30
50
80
mA
Output Leakage Current
IOUTOFF
VOUT = 24 V, Output State = Off
–
–
10
μA
RPU = 1 kΩ, CL = 4.7 nF, VPU = 5 V
–
10
–
μs
VPU = 5 V
0.8
1.1
1.5
μs
VPU = 12 V
–
1.6
–
μs
Output Rise Time
tr
Output Fall Time8
tf(OUT)
Measured from 90% to 10%,
TA = 25°C, RPU = 1 kΩ,
CL = 4.7 nF, (see figure 2)
Output Fall Time Variation with
Temperature
Δtf(OUT)
Maximum variation from TA = 25°C to
–40°C and then to 150°C
–
±20
–
%
Output Delay Time9
td(OUT)
4 kHz sinusoidal input signal, falling electrical
edge (see figure 2)
–
18
–
μs
TPOS functionality guaranteed
0.5
–
3.0
mm
Output switching in Running mode, TPOS
function not guaranteed
3.0
–
4.5
mm
Performance Characteristics
Operational Air Gap Range10
Extended Air Gap Range11
AGTPOS
AGEXTMAX
Analog Signal Bandwidth
BW
Equivalent to –3 dB cutoff frequency
–
20
–
kHz
Tooth Speed
fSIG
Tooth signal frequency, sinusoidal input signal
0
–
8000
Hz
Continued on the next page…
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
ATS675LSE
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS (continued) Valid using reference target 8X, TA , TJ , and VCC within specification, unless otherwise noted
Characteristics
Min.
Typ.1
Max.
Unit
–
1
3
edge
–
–
1
tooth
% of peak-to-peak, referenced to tooth signal
(see figure 4)
–
30
–
%pk–pk
% of peak-to-peak signal
–
10
–
%
Reduction in VPROC amplitude from VPROC(high)
to lowest peak VPROC(reduce), all specifications
within range (see figure 3)
–
–
15
%pk-pk
Reduction in VPROC amplitude from VPROC(high)
to lowest peak VPROC(reduce); output switches,
other specifications may be out of range (see
figure 3)
–
–
25
%pk-pk
ErrRELR
Rising mechanical edges after initial calibration,
gear speed = 1000 rpm, target eccentricity
< 0.1 mm
–
0.4
0.8
deg.
ErrRELF
Falling mechanical edges after initial calibration,
gear speed = 1000 rpm, target eccentricity
< 0.1 mm
–
0.5
1.0
deg.
Symbol
Test Conditions
Calibration7
Initial Calibration12,13
TPO to Running Mode Adjustment
CALI
Quantity of mechanical falling edges used to
determine Running mode switchpoints level
Quantity of mechanical falling edges after CALI
CALTPORM to transition from TPOS switchpoints level to
Running mode switchpoints level
Running Mode Switchpoint Characteristics
Running Mode Switchpoint
Internal Hysteresis
BST
BHYS(int)
Signal Characteristics
Maximum Allowable Signal Reduction14
Relative
Breduce
Timing Accuracy12,15
1Typical
values are at TA = 25°C and VCC = 12 V. Performance may vary for individual units, within the specified maximum and minimum limits.
voltage must be adjusted for power dissipation and junction temperature; see Power Derating section.
3Maximum current limit is equal to I (max) + 3 mA.
CC
4Negative current is defined as conventional current coming out of (sourced from) the specified device terminal.
5Sustained voltages beyond the clamp voltage may cause permanent damage to the IC.
6Power-On Time is the duration from when V
CC rises above VCC(min) until a valid output state is realized.
7For additional information see the Functional Description section.
8Characterization data shows 12 V fall time to be 1.5 times longer than 5 V fall time. See figure 2.
9Output Delay Time is the duration from when a crossing of the magnetic signal switching level, B , occurs to when the electrical output signal, V
ST
OUT ,
reaches 90% of VOUT(high).
10The Operational 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 opposite a tooth and correctly detecting a valley when powered-on opposite a valley, using reference target 8X.
11The Extended Air Gap Range is a range of installation air gaps, larger than AG
TPOS, within which the device will accurately detect target features in
Running mode, but TPOS functionality is NOT guaranteed, possibly resulting in undetected target features during Initial Calibration. Relative Timing
Accuracy (ErrREL) not guaranteed in Extended Air Gap Range.
12The term mechanical edge refers to a target feature, such as the side of a gear tooth, passing opposite the device. A rising edge is a transition from a
valley to a tooth, and a falling edge is a transition from a tooth to a valley. See figure 6.
13Signal frequency for CAL is f
I
SIG < 200 Hz.
14Running mode; 4X target used. The Processed Internal Signal, V
PROC , is the internal signal generated by the Hall detection circuitry and normalized
by Automatic Gain Control.
15Relative Timing Accuracy refers to the difference in accuracy, relative to a 0.5 mm air gap, through the entire Operational Air Gap Range, after initial
calibration; gear speed = 1000 rpm, target eccentricity < 0.1 mm. See figure 7.
2Maximum
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
Processed Input
Signal, VPROC
Definitions of Operating Characteristics
VPROC(high)
VPROC(BOP) ,
VPROC(BRP)
td(OUT)
VPROC(low)
Time
Output Signal, VOUT
tf(OUT)
VOUT(high)
90% VOUT
10% VOUT
VOUT(low)
Time
Figure 2. Definition of Output Delay Time, td(OUT) , and Output
Fall Time, tf(OUT) .
Highest peak
|B|
Signal
Reduction
Magnetic Signal, BSIG (G)
ATS675LSE
0
Breduce (%) =
Lowest peak
Time
BSIG Highest Peak – BSIG Lowest Peak
BSIG Highest Peak
× 100
Figure 3. Definition of Maximum Allowable Signal Reduction, Breduce , as a
percentage of the overall magnetic signal.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Characteristic Performance
Supply Current versus Ambient Temperature
Output Fall Time versus Ambient Temperature
RPU = 1 kΩ, CL = 4.7 nF
10
3.0
2.5
8
VCC (V)
7
3.3
15.0
24
tf(OUT) (μs)
ICC (mA)
9
1.0
5
0.5
-25
0
25
50
75
100
TA (°C)
125
150
0
-50
175
0.4
350
0.3
VOUT(sat) (mV)
IOUT (mA)
20
15
10
200
150
Edge Position (°)
400
250
50
75
100
TA (°C)
125
150
0.4
0.4
0.3
0.3
TA (°C)
-40
0
25
85
150
0
-0.1
-0.2
175
1
1.5
2
AG (mm)
2.5
3
3.5
0.2
Mechanical
Edge
Falling
Rising
0.1
0
-0.1
-0.2
-0.3
-0.4
0.5
150
Relative Timing Accuracy versus Speed
TA = 25°C, 1.5 mm Air Gap, Relative to 0.5 mm Air Gap
Edge Position (°)
Edge Position (°)
Relative Timing Accuracy versus Air Gap
Rising Mechanical Edge, 1000 rpm, Relative to 0.5 mm Air Gap
0.1
125
TA (°C)
-40
0
25
85
150
-0.4
0.5
175
0.2
75
100
TA (°C)
0
-0.3
25
50
-0.1
-0.2
0
25
0.1
50
-25
0
0.2
100
0
-50
-25
Relative Timing Accuracy versus Air Gap
Falling Mechanical Edge, 1000 rpm, Relative to 0.5 mm Air Gap
Output Voltage (Low) versus Ambient Temperature
300
5
12
24
1.5
6
4
-50
VPU (V)
2.0
-0.3
1
1.5
2
AG (mm)
2.5
3
3.5
-0.4
0
500
1000
1500
2000
2500
Gear Speed (rpm)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
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
2-layer PCB with copper limited to solder pads
and 3.57 in.2 of copper area each side
77
ºC/W
*Additional thermal information available on the Allegro website
Power Derating Curve
30
Maximum Allowable VCC (V)
25
VCC(max)
20
(RQJA = 77 ºC/W)
15
(RQJA = 101 ºC/W)
10
5
VCC(min)
0
20
40
60
80
100
120
140
160
180
Temperature, TA (ºC)
Power Dissipation, PD (mW)
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
(R
QJ
A
=
77
(R
QJ
20
40
60
A
=1
01
ºC
/W
ºC
/W
)
)
80
100
120
140
Temperature, TA (°C)
160
180
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Reference Target 8x
Test Conditions
Typ.
Unit
Do
Outside diameter of target
120
mm
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
23.6
mm
Circular Valley Length
tv
Length of valley, with respect to
branded face; measured at Do
23.6
mm
Tooth Whole Depth
ht
5
mm
–
–
Symbol Key
Branded Face
of Package
ØDO
ht
F
t
Outside Diameter
Symbol
tV
Characteristic
Material
CRS 1018
Air Gap
Branded Face
of Package
Reference Target 8X
Figure 4. Configuration with Reference Target
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Functional Description
Output Profile Polarity (LT/HT Option)
Device output, VOUT , is a digital representation of the mechanical profile of the target, as illustrated in figure 6. The customer
can choose the relative polarity of the output waveform. This
assigns the polarity opposite tooth features (the inverse polarity
Target (Gear)
Automatic Gain Control (AGC)
The Automatic Gain Control (AGC) feature ensures that the
ATS675 initial switching thresholds are isolated from the effects
of changes in the effective air gap (the total distance between
the Hall element and the nearest feature of the target). AGC is
implemented by unique patented self-calibrating circuitry, and
normalizes the sensed magnetic gradient so the internal processed
signal falls within the optimum processing range.
Device power-on
Target
Mechanical Profile
Tooth
Hall Technology
The ATS675 contains a single-chip Hall effect sensor IC, a 4-pin
leadframe, a specially designed rare-earth pellet, and a ferrous
pole piece (a precisely-mounted magnetic field concentrator).
The Hall IC supports a chopper stabilized Hall element that
measures the magnetic gradient created by the passing of a ferromagnetic object. This is illustrated in figure 5. The difference
in the magnetic gradients created by teeth and valleys allows the
devices to generate a digital output signal that is representative of
the target features.
will be output opposite valley features). The LT option sets VOUT
low when a tooth is opposite the device, and the HT option sets
VOUT high when a target tooth is opposite the device. This polarity assignment applies throughout device operation. This ease of
use reduces design time and incremental assembly costs for most
applications.
Valley
Internal Electronics
This device contains a self-calibrating Hall effect IC that includes
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. The
Hall IC supports a chopper stabilized Hall element that measures
the intensity of magnetic gradients and provides an electrical
signal that represents the target features.
|B|
Target
Magnetic Profile
0
V+
Processed
Input Signal, VPROC
0
LT option
(Inverting)
Output Switch State
On
Off On
Off
On
Off
On Off
Off On Off
On
Off On
VOUT = High
Low-B field
Hall element
Leadframe
High-B field
Hall IC
North Pole
Back-Biasing
Rare-Earth Pellet
Plastic
Pole piece
(Concentrator)
South Pole
VOUT = Low
HT option
(Following)
Output Switch State
VOUT = High
ATS Device
Off On
VOUT = Low
(A)
(B)
Figure 5. Application cross-section: (A) target tooth opposite device, and
(B) target valley opposite device
Figure 6. Output Profile Polarity options allow selection of VOUT either
inverted (LT option), or in-phase with the target profile (HT option), when
electrically connected as in figure 1.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
AGC is activated during the Initial Calibration stage at each
power-on. The device measures the peak-to-peak application
magnetic gradient, and then the gain of the sensor IC is adjusted
to normalize the internal processed signal, VPROC , to accommodate any input signal amplitude within the specified Operating
Magnetic Signal Range, BSIG . AGC is referenced to the internal
magnetic baseline. At the end of the Initial Calibration stage, the
AGC results are latched and they are not readjusted while the
device remains powered-on.
Power Supply Protection
The ATS675 provides features for protecting the device against
power supply aberrations:
Undervoltage Lockout When the supply voltage falls below
the undervoltage lockout level, VCCUV , the device Output State
changes to Off. The device remains in that state until the voltage level is restored to the VCC operating range. Changes in the
target magnetic gradient have no effect until that voltage level
is restored. This prevents false signals caused by undervoltage
conditions from propagating to the output of the sensor IC.
Processed Input Signal, VPROC (%)
EMC Protection The ATS675 contains an on-chip regulator
that operates throughout a wide range of supply voltage levels.
For applications using an unregulated power supply, protection
against transients may be added externally. For applications using
a regulated supply line, EMI and RFI protection may still be
required. Contact Allegro for information on EMC specification
compliance.
CALI
CALTPOSRM
Running Mode
Running mode
switchpoints for
I option
BTPOSHYS
TPOS switching
level
Time
Off
On
Off
On
VOUT
On
Figure 7. Calibration mode waveforms.
Off
Output State
for HT option
Operating Modes
The device provides three operating modes: TPOS, Calibration,
and Running. TPOS and Calibration initialize simultaneously at
power-on. TPOS generates immediate device output, controlling
device switching while the calibration functions are performed.
After calibration is complete, normal operation in Running mode
begins.
TPOS (True Power-On State) Operation
After the power-on time, tPO , the device immediately generates
an output voltage corresponding to the target feature opposite the
device. It does so by comparing the existing level of the application magnetic gradient, BAPP , to the TPOS switching level,
an internal threshold used to distinguish a tooth from a valley
during TPOS operation (from power-on until the end of the Initial
Calibration stage). If BAPP is less than the threshold, that target
feature is evaluated as a valley, and if BAPP is greater , the feature
is evaluated as a tooth.
Calibration Mode Operation
At power-on (simultaneous with TPOS operation) Calibration
mode begins. Calibration mode is performed in two stages: the
Initial Calibration stage, followed immediately by the TPOS to
Running Mode Transition stage (see figure 7). After the second
calibration stage, Running mode begins immediately.
In Calibration mode, the operating range of the application
magnetic gradient, BAPP , is detected and evaluated, and then the
ATS675 electronics are adapted for optimal output switching.
Calibration is performed quickly, without reading the entire target, because the ATS675 applies the internal magnetic baseline.
Initial Calibration Stage During the Initial Calibration stage,
TPOS operation controls device output switching while calibration starts. In this stage, the peak-detecting DACs acquire the
application magnetic signal. Based on those results, the Automatic Gain Control (AGC) feature calculates the normalized
Running mode switching range. This period is minimized, so
swapping to the Running mode thresholds can occur as quickly as
possible.
TPOS to Running Mode Transition Stage At the beginning
of this stage, TPOS operation terminates, and throughout this
stage the device automatically adjusts the output switching levels
from the original preset switching level to the Running mode
switchpoints. This transition takes place over one tooth, immediately swapping from TPOS to Running mode switchpoints.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Running Mode Operation
Running mode begins immediately at the end of Calibration
mode. During Running mode, switchpoints are established
dynamically, based on the sensed application magnetic gradient, BAPP . To determine switchpoints, BAPP is normalized by the
AGC feature, and processed to generate the internal processed
signal, VPROC . Two peak-detecting DACs track the VPROC waveform, and the output switchpoints are established as percentages
of the values held by the two DACs. Because the switchpoints
are established dynamically as a percentage of the peak-to-peak
signal, the effects of an application baseline shift are minimized.
Running Mode Switchpoints
The values used to define Running mode switchpoints are cal-
culated as a percentage of the peak-to-peak VPROC . As shown in
figure 11, this percentage is subtracted from the maximum VPROC
value, VPROC(high) , a value corresponding to a minimum air gap,
that is, at the most prominent target tooth. On the ATS675LSE,
the switchpoints are referenced to approximately 30% of the
peak-to-peak magnetic signal. This level closely corresponds to
the mechanical target edges, resulting in optimal timing accuracy
versus air gap.
Running Mode Hysteresis
The ATS675LSE uses an internal hysteresis method, switching at
a consistent point on both rising and falling edges. When a target
anomaly is encountered, the internal hysteresis thresholds provide
immunity to false switching, as illustrated in figure 12.
Operating Magnetic Signal, BSIG
Application Magnetic Gradient, BAPP
BST
BHYS
BHYS
VPROC(low)
Application and internal baseline
100
Processed Input Signal, VPROC (%)
VPROC(high)
|B|
0
Processed Input Signal,
VPROC (%)
Target
Mechanical
Profile
VPROC(high)
BST
+BHYS(int)
Switchpoints Level
–BHYS(int)
VPROC(low)
On
Off
On
Off
Time
Output State
for LT option
0
Time
Figure 11. Switchpoints Level for Running Mode definition
(switchpoints indicated by circles).
Figure 12. Running mode switching on anomalous peak
(switchpoints indicated by circles).
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
ATS675LSE
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
Power Derating
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 website.)
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
(1)
ΔT = PD × RθJA
(2)
TJ = TA + ΔT
(3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 7 mA, and RJA = 77 °C/W, then:
Example: Reliability for VCC at TA = 150°C.
Observe the worst-case ratings for the device, specifically:
RJA = 101 °C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 10 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
T(max) = 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) = T(max) ÷ RJA = 15°C ÷ 101 °C/W = 148.5 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 148.5 mW ÷ 10 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 RJA. If VCC(est) ≥ VCC(max), then operation between
VCC(est) and VCC(max) is reliable under these conditions.
PD = VCC × ICC = 12 V × 7 mA = 84 mW

T = PD × RJA = 84 mW × 77 °C/W = 6.5°C
TJ = TA + T = 25°C + 6.5°C = 31.5°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, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
Self-Calibrating TPOS Speed Sensor IC
Optimized for Automotive Cam Sensing Applications
ATS675LSE
Package SE 4-Pin SIP
7.00±0.05
B
E
10.00±0.05
LLLLLLL
NNN
YYWW
3.3±0.1
F
Branded
Face
D
A
4.9±0.1
1
6.23±0.10
2
3
Standard Branding Reference View
= 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
1.3±0.1
4
0.9±0.1
+0.06
0.38 –0.04
24.65±0.10
0.60±0.10
For Reference Only, not for tooling use (reference DWG-9001)
Dimensions in millimeters
A Dambar removal protrusion (16X)
11.60±0.10
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
1.0 REF
C Thermoplastic Molded Lead Bar for alignment during shipment
D Branding scale and appearance at supplier discretion
2.00±0.10
E Active Area Depth, 0.43 mm
F Hall element (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
Copyright ©2008-2013, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC 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, LLC 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, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
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