ATS642 Datasheet

ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Features and Benefits
Description
▪ Running mode calibration for continuous optimization
▪ Single chip IC for high reliability
▪ Internal current regulator for 2-wire operation
▪ Small mechanical size (8 mm diameter × 5.5 mm depth)
▪ Precise duty cycle signal over operating temperature range
▪ Large operating air gaps
▪ Automatic Gain Control (AGC) for air gap independent
switchpoints
▪ Automatic Offset Adjustment (AOA) for signal processing
optimization
▪ True zero-speed operation
▪ Undervoltage lockout
▪ Wide operating voltage range
The ATS642LSH is an optimized Hall effect sensing integrated
circuit and magnet combination that provides a user-friendly
solution for true zero-speed digital gear-tooth sensing in twowire applications. The sensor consists of a single-shot molded
plastic package that includes a samarium cobalt magnet, a
pole piece, and a Hall effect IC that has been optimized to the
magnetic circuit. This small package, with optimized two-wire
leadframe, can be easily assembled and used in conjunction
with a wide variety of gear shapes and sizes.
Package: 4-pin Module (suffix SH)
The integrated circuit incorporates a dual element Hall effect
sensor and signal processing that switches in response to
differential magnetic signals created by ferrous gear teeth.
The circuitry contains a sophisticated digital circuit to reduce
magnet and system offsets, to calibrate the gain for air gap
independent switchpoints, and to achieve true zero-speed
operation. Signal optimization occurs at power-up through
the combination of offset and gain adjust and is maintained
throughout the operating time with the use of a running mode
calibration. The running mode calibration allows immunity to
environmental effects such as microoscillations of the target
or sudden air gap changes.
The regulated current output is configured for two wire
applications and the sensor is ideally suited for obtainContinued on the next page…
Engineering samples available on a limited basis. Contact your local
sales or applications support office for additional information.
Not to scale
Functional Block Diagram
Hall
Amplifier
Automatic Offset
Control
VCC
Gain
AOA DAC
AGC DAC
Internal Regulator
Gain Control
Tracking
DAC
Peak Hold
GND
Test Signals
ATS642LSH-DS, Rev. 1
Test
ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Description (continued)
ing speed and duty cycle information in ABS (antilock braking
systems). The 1.5 mm Hall element spacing is optimized for fine
pitch gear-tooth-based configurations. The package is lead (Pb)
free, with 100% matte tin leadframe plating.
Selection Guide
Part Number
ICC Typical
Packing*
ATS642LSHTN-I1-T
6.0 Low to 14.0 High mA
ATS642LSHTN-I2-T
7.0 Low to 14.0 High mA
*Contact Allegro™ for additional packing options
Tape and reel, 13-inch reel 800 pieces/reel
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Unit
Supply Voltage
VCC
28
V
Reverse_Supply Voltage
VRCC
–18
V
–40 to 150
ºC
Range L
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Storage Temperature
Pin-out Diagram
1 2 3 4
Terminal List
Number
Name
1
VCC
2
NC
3
Test pin
4
GND
Function
Connects power supply to chip
No connection
Float or tie to GND
Ground terminal
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115 Northeast Cutoff
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
OPERATING CHARACTERISTICS using reference target 60-0, TA and VCC within specification, unless otherwise noted
Characteristic
Min.
Typ.1
Max.
Units
4.0
–
24
V
VCC 0 → 5 V and 5 → 0 V
–
–
4.0
V
Symbol
Test Conditions
ELECTRICAL CHARACTERISTICS
Supply Voltage2
Undervoltage Lockout
VCC
VCC(UV)
Operating; TJ < 165 °C
Supply Zener Clamp Voltage
VZ
ICC = ICC(max) + 3 mA; TA = 25°C
28
–
–
V
Supply Zener Current
IZ
Test conditions only; VZ = 28 V
–
–
ICC(max)+
3 mA
mA
ATS642LSH-I1
4.0
6.0
8.0
mA
ATS642LSH-I2
5.9
7.0
8.4
mA
ATS642LSH-I1
12.0
14.0
16.0
mA
ATS642LSH-I2
11.8
14.0
16.8
mA
1.85
–
3.05
–
VRCC = –18 V
–
–
–5
mA
t > tPO
–
ICC(High)
–
–
ICC(Low)
Supply Current
ICC(High)
Supply Current Ratio
Reverse Battery Current
ICC(High)/ Ratio of high current to low current
ICC(Low)
IRCC
POWER-ON STATE CHARACTERISTICS
Power-On State3
POS
Power-On Time4
tPO
Target gear speed < 100 rpm
–
1
2
ms
dI/dt
RLOAD = 100 Ω, CLOAD = 10 pF
–
10
–
mA/μs
OUTPUT STAGE
Output Slew Rate5
Continued on the next page.
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
OPERATING CHARACTERISTICS (continued) using reference target 60-0, TA and VCC within specification, unless otherwise noted
Characteristic
Symbol
Test Conditions
Min.
Typ.1
Max.
Units
SWITCHPOINT CHARACTERISTICS
Rotation Speed
SROT
Reference Target 60-0
0
–
8,000
rpm
BW
Equivalent to f – 3 dB
20
40
–
kHz
–
120
–
mV
–
120
–
mV
Quantity of rising output (current) edges required for
accurate edge detection
–
–
3
Edge
Output switching only; may not meet datasheet specications
–
±60
–
G
0.5
–
2.75
mm
–
–
3
mm
41
–
61
%
AG = 1.5 mm
–
±1.5
–
%
Sig
Operating within specification
30
–
1000
G
SigOP(min)
Output switching (no missed edges); ∆DC not guaranteed
20
–
–
G
Analog Signal Bandwidth
Operate Point
BOP
Release Point
BRP
Transitioning from ICC(High) to ICC(Low); positive peak
referenced; AG < AGMAX
Transitioning from ICC(Low) to ICC(High); negative peak
referenced; AG < AGMAX
CALIBRATION
Initial Calibration
CI
DAC CHARACTERISTICS
Allowable User-Induced Differential
Offset
FUNCTIONAL CHARACTERISTICS6
Operational Air Gap Range7
Maximum Operational Air Gap
Range
AG
AGOP(max)
Duty Cycle Variation
∆DC
Duty Cycle Pitch Variance8
EDC
Operating Signal Range9
Minimum Operating Signal
∆DC within specification
Output switching (no missed edges); ∆DC not guaranteed
Wobble < 0.5 mm; Typical value at AG = 1.5 mm, for
max., min., AG within specification
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.
3Please refer to Sensor Operation section, page 13.
4Power-On Time includes the time required to complete the internal automatic offset adjust. The DACs are then ready for peak acquisition.
5dI is the difference between 10% of I
CC(Low) and 90% of ICC(High), and dt is time period between those two points.
Note: di/dt is dependent upon the value of the bypass capacitor, if one is used.
6Functional characteristics valid only if magnetic offset is within the specified range for Allowable User Induced Differential Offset.
7AG is dependent on the available magnetic field. The available field is dependent on target geometry and material, and should be independently characterized. The field available from the reference target is given in the reference target parameter section of the datasheet.
8E
DC represents the difference between consecutive duty cycles, DC(n) - DC(n-1); Mean ± 3-sigma.
9In order to remain in specification, the magnetic gradient must induce an operating signal greater than the minimum value specified. This includes the
effect of target wobble.
2Maximum
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Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
REFERENCE TARGET, 60-0 (60 Tooth Target)
Characteristics
Symbol
Test Conditions
Typ.
Units
Do
Outside diameter of target
120
mm
Face Width
F
Breadth of tooth, with
respect to sensor
6
mm
Angular Tooth Thickness
t
Length of tooth, with
respect to sensor
3
deg
Angular Valley Thickness
tv
Length of valley, with
respect to sensor
3
deg
Tooth Whole Depth
ht
3
mm
–
–
Outside Diameter
Material
Low Carbon Steel
Symbol Key
t
Do
ht
F
tv
Air Gap
Branded Face of Sensor
Reference Gear Magnetic Gradient Amplitude
With Reference to Air Gap
800
600
500
400
300
200
Branded Face
of Sensor
100
0
0.5
1
1.5
2
2.5
Reference Target
60-0
3
Air Gap (mm)
Reference Gear Magnetic Profile
Two Tooth-to-Valley Transitions
500
Air Gap
400
(mm)
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
300
Differential B* (G)
Peak-to-Peak Differential B (G)
700
200
100
0
-100
-200
3.00 mm AG
-300
0.50 mm AG
-400
-500
0
2
4
6
8
10
12
Gear Rotation (°)
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Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
Characteristic Data
I1 Trim
Supply Current (High) versus Supply Voltage
(ATS642-I1)
16
16
15
15
VCC (V)
24
12
4
14
ICC(HIGH) (mA)
ICC(HIGH) (mA)
Supply Current (High) versus Ambient Temperature
(ATS642-I1)
TA (°C)
-40
25
85
150
14
13
13
12
12
-50
0
50
100
0
150
5
10
TA (°C)
Supply Current (Low) versus Ambient Temperature
(ATS642- I1)
20
25
Supply Current (Low) versus Supply Voltage
(ATS642-I1)
8
8
7
7
Vcc (V)
24
12
4
6
ICC(LOW) (mA)
ICC(LOW) (mA)
15
VCC (V)
TA (°C)
-40
25
150
6
5
5
4
4
-50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
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Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
Duty Cycle versus Air Gap*
61
59
57
DC (%)
55
53
TA (°C)
-40
25
150
51
49
47
45
43
41
0.5
1.0
1.5
2.0
2.5
3.0
AG (mm)
*The trend of duty cycle versus air gap is driven by the actual magnetic profile of the
target (see figure on page 5).
Duty Cycle Variance versus Air Gap
Mean ± 3 Sigma, 25°C
Duty Cycle versus Ambient Temperature
61
6
59
57
4
53
AG (mm)
0.5
1.5
2.75
51
49
47
45
2
0
-2
-4
43
41
–50
EDC (%)
DC (%)
55
-6
0
50
TA (°C)
100
150
0.5
1.0
1.5
2.0
2.5
3.0
AG (mm)
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Characteristic Allowable Air Gap Movement
60-0 (60 Tooth Target)
Allowable Air Gap Movement from TEAGCAL
1.2
$TEAGOUT (mm)
1.0
0.8
0.6
0.4
0.2
0
-0.2
0
0.2
0.4
0.6
0.8
1.0
$TEAGIN (mm)
The colored area in the chart above shows the region of allowable air gap movement within which the sensor will continue
output switching. The output duty cycle is wholly dependent on
the target’s magnetic signature across the air gap range of movement, and may not always be within specification throughout the
entire operating region (to AG(OPmax)).
(a)
1.2
1.4
1.8
The axis parameters for the chart are defined in the drawings below. As an example, assume the case where the air gap
is allowed to vary from from the nominal installed air gap
(TEAGCAL , panel a) within the range defined by an increase of
∆TEAG OUT = 0.35 mm (shown in panel b), and a decrease of
∆TEAG IN = 0.65 mm (shown in panel c). This case is plotted
with an “x” in the chart above.
(b)
Sensor
1.6
(c)
Sensor
TEAGCAL
TEAG OUT
TEAG IN
Sensor
For more information on these figures and the calculations used to generate them, please refer to the Applications
Note Determining Allowable Air Gap Variation for the ATS642.
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions*
Single-layer PCB with copper limited to solder pads
RθJA
Package Thermal Resistance
in.2
Two-layer PCB with 3.8
of copper area on each side connected with thermal vias and to device ground pin
Value
Units
126
ºC/W
84
ºC/W
*Additional information is available on the Allegro Web site.
Maximum Allowable VCC (V)
Power Derating Curve
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
VCC(max)
(RQJA = 84 ºC/W)
(RQJA = 126 ºC/W)
VCC(min)
20
40
60
80
100
120
140
160
180
Temperature (ºC)
Power Dissipation, PD (m W)
Maximum Power Dissipation, PD(max)
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
(R
QJ
(R
QJ
20
40
60
A
=1
26
ºC
A
=
/W
84
ºC
/W
)
)
80
100
120
Temperature (°C)
140
160
180
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115 Northeast Cutoff
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Functional Description
Sensing Technology
Output Polarity
The gear tooth sensor subassembly contains a single-chip differential Hall effect sensor IC, an optimized samarium cobalt
magnet, and a flat ferrous pole piece. The Hall IC possesses two
Hall elements, which sense the magnetic profile of the ferrous
target simultaneously, but at different points (spaced at a 1.5 mm
pitch), generating a differential internal analog voltage (VPROC)
that is processed for precise switching of the digital output
signal.
Figure 3 shows the output polarity for the orientation of target
and sensor shown in figure 2. The target direction of rotation shown is: perpendicular to the leads, across the face of the
device, from the pin 1 side to the pin 4 side. This results in the
sensor output switching from high, ICC(High), to low ICC(Low), as
the leading edge of a tooth (a rising mechanical edge, as detected
by the sensor) passes the sensor face. In this configuration, the
device output current switches to its low polarity when a tooth is
the target feature nearest to the sensor. If the direction of rotation is reversed, then the output polarity inverts.
The Hall IC is self-calibrating and also possesses a temperature
compensated amplifier and offset compensation circuitry. Its
voltage regulator provides supply noise rejection throughout the
operating voltage range. Changes in temperature do not greatly
affect this device due to the stable amplifier design and the offset
compensation circuitry. The Hall transducers and signal processing electronics are integrated on the same silicon substrate, using
a proprietary BiCMOS process.
Target Profiling
An operating device is capable of providing digital information
that is representative of the mechanical features on a rotating
target. The waveform diagram shown in figure 3 presents the
automatic translation of the mechanical profile, through the
magnetic profile that it induces, to the digital output signal of the
sensor.
Note that output voltage polarity is dependent on the position of
the sense resistor, RSENSE (see figure 4).
Target
Mechanical Profile
Representative
Differential
Magnetic Profile
Sensor Electrical
Output Profile, IOUT
Figure 3. Output Profile of a ferrous target for the polarity indicated in
figure 2.
VSUPPLY
VCC
Target (Gear)
RSENSE
Element Pitch
Hall Element 2
Dual-Element
Hall Effect Device
ICC
VOUT(H)
Hall Element 1
Hall IC
Pole Piece
(Concentrator)
South Pole
Back-biasing Magnet
North Pole
Case
(Pin 4 Side)
(Pin 1 Side)
1
1
VCC
VCC
ATS642
ATS642
GND
4
GND
4
VOUT(L)
Figure 1. Relative motion of the target is detected by the dual Hall elements mounted on the Hall IC.
ICC
RSENSE
Branded Face
of Sensor
Rotating Target
I+
IOUT
V+
1
4
VOUT(L)
V+
Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation
results in a low output signal when a tooth of the target gear is nearest
the face of the sensor (see figure 3). A right-to-left (pin 4 to pin 1) rotation inverts the output signal polarity.
VOUT(H)
Figure 4: Voltages profiles for high side and low side two-wire sensing.
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ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Automatic Gain Control (AGC)
This feature allows the device to operate with an optimal internal
electrical signal, regardless of the air gap (within the AG specification). During calibration, the device determines the peak-topeak amplitude of the signal generated by the target. The gain of
the sensor is then automatically adjusted. Figure 5 illustrates the
effect of this feature.
Automatic Offset Adjust (AOA)
The AOA is patented circuitry that automatically compensates
for the effects of chip, magnet, and installation offsets. (For
capability, see Dynamic Offset Cancellation, in the Operating Characteristics table.) This circuitry is continuously active,
including both during calibration mode and running mode, compensating for any offset drift. Continuous operation also allows it
to compensate for offsets induced by temperature variations over
time.
Digital Peak Detection
A digital DAC tracks the internal analog voltage signal VPROC,
and is used for holding the peak value of the internal analog
signal. In the example shown in figure 6, the DAC would first
track up with the signal and hold the upper peak’s value. When
VPROC drops below this peak value by BOP, the device hysteresis, the output would switch and the DAC would begin tracking
the signal downward toward the negative VPROC peak. Once the
DAC acquires the negative peak, the output will again switch
states when VPROC is greater than the peak by the value BRP. At
this point, the DAC tracks up again and the cycle repeats. The
digital tracking of the differential analog signal allows the sensor
to achieve true zero-speed operation.
Ferrous Target
Mechanical Profile
V+
Internal Differential
Analog Signal
Response, without AGC
V+
AGLarge
Internal
Differential
Analog Signal
BOP
BRP
AGSmall
V+
Internal Differential
Analog Signal
Response, with AGC
I+
AGSmall
AGLarge
Figure 5. Automatic Gain Control (AGC). The AGC function corrects for
variances in the air gap. Differences in the air gap affect the magnetic
gradient, but AGC prevents that from affecting device performance, a
shown in the lowest panel.
Device
Output Current
Figure 6: Peak Detecting Switchpoint Detail
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Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
Power Supply Protection
Assembly Description
The device contains an on-chip regulator and can operate over
a wide VCC range. For devices that need to operate from an
unregulated power supply, transient protection must be added
externally. For applications using a regulated line, EMI/RFI protection may still be required. Contact Allegro Microsystems for
information on the circuitry needed for compliance with various
EMC specifications. Refer to figure 7 for an example of a basic
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.
application circuit.
Undervoltage Lockout
When the supply voltage falls below the undervoltage lockout
voltage, VCC(UV), the device enters Reset, where the output state
returns to the Power-On State (POS) until sufficient VCC is supplied. ICC levels may not meet datasheet limits when
VCC < VCC(min).
Diagnostics
The regulated current output is configured for two-wire applications, requiring one less wire for operation than do switches
with the more traditional open-collector output. Additionally,
the system designer inherently gains diagnostics because there is
always output current flowing, which should be in either of two
narrow ranges, shown in figure 8 as ICC(High) and ICC(Low). Any
current level not within these ranges indicates a fault condition. If ICC > ICC(High)max, then a short condition exists, and if
ICC < ICC(low)min, then an open condition exists. Any value of ICC
between the allowed ranges for ICC(High) and ICC(Low) indicates a
general fault condition.
V+
1
VCC
ATS642
Pins 2 and 3 floating
GND
4
CBYP
0.01 μF
+mA
ICC(High)max
ICC(High)min
ICC(Low)max
ICC(Low)min
ECU
100 7
RSENSE
Figure 7: Typical Application Circuit
Short

Range for Valid ICC(HIGH)

Range for Valid ICC(LOW)
Fault
Open
0
Figure 8: Diagnostic Characteristics of Supply Current Values
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Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
AGC is active, and selects the optimal signal gain based on the
amplitude of the VPROC signal. Following each adjustment to
the AGC DAC, the Offset DAC is also adjusted to ensure the
internal analog signal is properly centered.
Sensor Operation
Each operating mode is described in detail below.
Power-On
When power (VCC > VCCMIN) is applied to the device, a short
period of time is required to power the various portions of the
IC. During this period, the ATS642 will power-on in the high
current state, ICC(High). After power on, there are conditions that
could induce a change in the output state. Such an event could be
caused by thermal transients, but would require a static applied
magnetic field, proper signal polarity, and particular direction
and magnitude of internal signal drift.
During this mode, the tracking DAC is active and output switching occurs, but the duty cycle is not guaranteed to be within
specification.
Running Mode
After the Initial Calibration period, CI, establishes a signal gain,
the device moves to Running mode. During Running mode, the
sensor tracks the input signal and gives an output edge for every
peak of the signal. AOA remains active to compensate for any
offset drift over time.
Initial Offset Adjust
The sensor intially cancels the effects of chip, magnet, and
installation offsets. Once offsets have been cancelled, the digital
tracking DAC is ready to track the signal and provide output
switching. The period of time required for both Power-On and
Initial Offset Adjust is defined as the Power-On Time.
The ATS642 incorporates a novel algorithm for adjusting the
signal gain during Running mode. This algorithm is designed
to optimize the VPROC signal amplitude in instances where the
magnetic signal “seen” during the calibration period is not representative of the amplitude of the magnetic signal for the installed
sensor air gap (see figure 9).
Calibration Mode
The calibration mode allows the sensor to automatically select
the proper signal gain and continue to adjust for offsets. The
1
2
3
4
5
BOP
Internal Differential
Signal, VPROC
BOP
BRP
BRP
Sensor Electrical
Output, IOUT
Figure 9: Operation of Running Mode Gain Adjust.
Position 1. The device is initially powered-on. Self-calibration occurs.
Position 2. Small amplitude oscillation of the target sends an erroneously small differential signal to the sensor. The amplitude of VPROC is greater than the switching hysteresis (BOP and BRP), and the device output switches.
Position 3. The calibration period completes on the third rising output edge, and the device enters Running mode.
Position 4. True target rotation occurs and the correct magnetic signal is generated for the installation air gap. The established signal gain is too large for the target’s rotational magnetic signal at the given air gap.
Position 5. Running Mode Calibration corrects the signal gain to an optimal level for the installation air gap.
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13
ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
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 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, Rθ JC, 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 × Rθ JA
(2)
TJ = TA + ΔT
(3)
Example: Reliability for VCC at TA = 150°C, package SH
(I1 trim), using minimum-K PCB
Observe the worst-case ratings for the device, specifically:
Rθ JA = 126°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 16 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = ΔTmax ÷ RθJA = 15°C ÷ 126 °C/W = 119 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 119 mW ÷ 16 mA = 7 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
Rθ JA. 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,
VCC = 12 V, ICC = 4 mA, and RθJA = 140 °C/W, then:
PD = VCC × ICC = 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 (VCC(max), ICC(max)), without exceeding TJ(max),
at a selected Rθ JA and TA.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
ATS642LSH
Package SH Module
5.50±0.05
F
0.75
F
E
0.75
B
8.00±0.05
LLLLLLL
NNN
5.80±0.05
E1
E2
YYWW
Branded
Face
1.70±0.10
5.00±0.10
D
4.00±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-9003)
Dimensions in millimeters
A Dambar removal protrusion (16X)
24.65±0.10
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
C Thermoplastic Molded Lead Bar for alignment during shipment
+0.06
0.38 –0.04
1.00±0.10
13.10±0.10
D Branding scale and appearance at supplier discretion
E Active Area Depth 0.43 mm REF
F
Hall elements (E1, E2); not to scale
A
1.0 REF
1.60±0.10
C
1.27±0.10
0.71±0.10
0.71±0.10
5.50±0.10
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
ATS642LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor with Continuous Calibration
Copyright ©2004-2013, 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 any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
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
16
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