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 ATS675LSE Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Features and Benefits
Chopper stabilized; optimized for automotive cam sensing applications Optimized absolute timing accuracy step size through gradual transition from TPOS to Running Mode High immunity to signal anomalies resulting from magnetic overshoot and peak-to-peak field variation Tight timing accuracy over full operating temperature range True zero-speed operation Automatic Gain Control circuitry for air gap independent switchpoints Operation at supply voltages down to 3.3 V Digital output representing target profile Undervoltage lockout (UVLO) Patented Hall IC-magnet system Increased output fall time for improved radiated emissions performance
Description
The ATS675 is the next generation of the Allegro(R) True Power-On State (TPOS) sensor family, offering improved accuracy compared to prior generations, gradual TPOS to Running Mode adjustment for accuracy-shift reduction, and longer output fall time for improved radiated emissions performance. The ATS675 provides absolute zero-speed performance and TPOS information. The sensor incorporates a single-element Hall IC with an optimized custom magnetic circuit that switches in response to magnetic signals created by a ferromagnetic 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 device performance at zero target speed, independent of air gap, and which adapts dynamically to the typical operating conditions found in automotive applications, particularly camshaft-sensing applications. High resolution peak-detecting DACs are used to set the adaptive switching thresholds of the device, ensuring high accuracy despite target eccentricity. Internal hysteresis in the thresholds reduces the negative effects of anomalies in the magnetic signal (such as magnetic overshoot) associated with targets used in many automotive applications. The resulting output of the device is a digital representation of the ferromagnetic target profile. The ATS675 also includes a low bandwidth filter that increases the noise immunity and the signal-to-noise ratio of the sensor. The device package is lead (Pb) free, with 100% matte tin leadframe plating.
Package: 4-pin SIP module (suffix SE)
1
Not to scale
2 3 4
Typical Application
VS CBYPASS
0.1 F 1 VCC 3 A
VPU RPU
2
ATS675
TEST GND 4 OUT
Sensor Output CL
A Recommended
Figure 1. Operational circuit for the ATS675 ATS675LSE-DS
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Selection Guide
Part Number Output Protocol Packing*
13-in. reel, 450 pieces per reel ATS675LSETN-LT-T Output low opposite target tooth ATS675LSETN-HT-T Output high opposite target tooth *Contact Allegro for additional packing options
Absolute Maximum Ratings
Characteristic Supply Voltage Reverse Supply Voltage Reverse Supply Current Output Current Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VCC VRCC IRCC IOUT(sink) TA TJ(max) Tstg Internal current limiting is intended to protect the device from output short circuits, but is not intended for continuous operation. Range L Notes Rating 28 -18 -50 20 -40 to 150 165 -65 to 170 Units V V mA mA C C C
Thermal Characteristics may require derating at maximum conditions, see application information
Characteristic
Package Thermal Resistance
Symbol
RJA
Test Conditions*
1-layer PCB with copper limited to solder pads 2-layer PCB with copper limited to solder pads and 3.57 in.2 of copper area each side
Value
101 77
Units
C/W C/W
*Additional thermal information available on the Allegro website
Power Derating Curve
30
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 20 40 60
25
Maximum Allowable VCC (V)
VCC(max)
Power Dissipation, PD (mW)
20
(R
JA
(R
15
JA
= 77 C/W) = 101 C/W)
=
77
C
(R
10
(R
JA
/W
)
JA
=1
01
C
/W
)
5
VCC(min)
0 20
40
60
80
100
120
140
160
180
Temperature, TA (C)
80 100 120 140 Temperature, TA (C)
160
180
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
2
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Functional Block Diagram
VCC Multiplexed Test Signals Internal Regulator (Analog) Internal Regulator (Digital) Oscillator Baseline Trim NDAC
TEST
Update Logic
Running Mode Threshold Selector OUT
PDAC
Hall Amp
+/ -
Low Pass Filter
+/ -
DDA
Mode Control
Current Limit
Temperature Compensation Trim
Auto Gain Adjust
Dynamic Threshold DAC TPOS
TPOS Trim
GND
Pin-out Diagram Terminal List
Number 1 2 3 4 Name VCC OUT TEST GND Supply voltage Open drain output Test pin; connection to GND recommended Ground Function
12
3
4
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
3
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS Valid using reference target 8X, TA ,TJ , and VCC within specification, unless otherwise noted
Characteristics Electrical Characteristics Supply Voltage2 Undervoltage Lockout Supply Zener Clamp Voltage Supply Zener Current3 Supply Current Reverse Battery Current4 Chopping Frequency Power-On Characteristics Power-On Time5 Output Stage Characteristics Output On Voltage Output Zener Voltage Output Current Limit Output Leakage Current Output Delay Time6 Output Rise Time Output Fall Time7 Output Fall Time Variation Over Temperature Range VOUT(SAT) VZOUT IOUTLIM IOUTOFF td tr tf tf IOUT = 10 mA, output in on-state IOUT = 15 mA, output in on-state IOUT = 3 mA, TA = 25C Output in on-state VOUT = 24 V, output in off-state 4 kHz sinusoidal signal, falling electrical edge RPU = 1 k, CL = 4.7 nF, VPU = 5 V TA = 25C, RPU = 1 k, CL = 4.7 nF VPU = 5 V VPU = 12 V - - 30 30 - - - 5 - - - - - - 0.5 3.0 - - - - 50 0.1 22 10.3 8 15 0.2 High Low Low High - - 0.4 400 450 - 80 10 - - 15 - - - - - - 3.0 4.5 0.8 mV mV V mA A s s s s %/C V V V V mm mm deg. tPO VCC > VCC(min), fSIG < 200 Hz - - 1 ms VCC VCCUV VZsupply IZsupply ICC IRCC fc VRCC = -18 V Operating, TJ < TJ(max) VCC = 0 5 V or 5 0 V ICC = ICC(max) + 3 mA, TA = 25C VS = 28 V 3.3 - 28 - - - - - - 33 - 6.5 -5 500 24 3.3 40 13 10 -10 - V V V mA mA mA kHz Symbol Test Conditions Min. Typ.1 Max. Unit
Maximum variation from TA = 25C HT device package option Opposite target tooth Opposite target valley Opposite target tooth Opposite target valley
Output Polarity
VOUT
LT device package option
Performance Characteristics Operational Air Gap Range8 Extended Air Gap Range9 AGTPOS AGEXTMAX ErrRELR Relative Timing Accuracy10,11 ErrRELF TPOS functionality guaranteed Output switching in Running Mode, TPOS function not guaranteed Rising mechanical edges after initial calibration, gear speed = 1000 rpm, target eccentricity < 0.1 mm Falling mechanical edges after initial calibration, gear speed = 1000 rpm, target eccentricity < 0.1 mm
-
0.5
1.0
deg.
Continued on the next page...
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
4
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS (continued) Valid using reference target 8X, TA , TJ , and VCC within specification, unless otherwise noted
Characteristics Tooth Speed Analog Signal Bandwidth Switchpoint Characteristics Switchpoint Internal Hysteresis12 Calibration Initial Calibration13 TPO to Running Mode Adjustment Signal Characteristics Breduce(G) Maximum Allowable Signal Reduction14 Breduce(NG)
1Typical
Symbol fSIG BW
Test Conditions Tooth signal frequency, sinusoidal input signal Equivalent to -3 dB cutoff frequency % of peak-to-peak, referenced to tooth signal (see figure 4) % of peak-to-peak signal Quantity of mechanical falling edges during which device is in full TPOS Mode
Min. 0 -
Typ.1 - 20
Max. 8000 -
Unit Hz kHz
BST BHYS
- -
30 10
- -
% %
CALI
- 1
- -
4 16
Edges Teeth
Quantity of target teeth after CALI over which CALTPORM TPOS to Running Mode threshold adjustment occurs Reduction in VPROC amplitude from VPROC(high) to lowest peak VPROC(reduce), all specifications within range (see figure 5) Reduction in VPROC amplitude from VPROC(high) to lowest peak VPROC(reduce); output switches, other specifications may be out of range (see figure 5)
-
-
15
%pk-pk
-
-
25
%pk-pk
values are at TA = 25C 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. 5Power-On Time is the duration from when V CC rises above VCC(min) until a valid output state is realized. 6Output Delay Time is the duration from when a crossing of the magnetic signal switchpoint, B , occurs to when the electrical output signal, V ST OUT , reaches 90% of VOUT(high). 7Characterization data shows 12 V fall time to be 1.5 times longer than 5 V fall time. See figure 2. 8The 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. 9The 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. 10The 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 7. 11Relative Timing Accuracy refers to the difference in accuracy, relative to a 0.5 mm air gap, through the entire Operational Air Gap Range. See figure 7. 12Refer to Functional Description section for a description of Internal Hysteresis. 13Signal frequency, f SIG < 200 Hz. 14Running Mode; 4X target used. The Operational Signal Amplitude, V PROC , is the internal signal generated by the Hall detection circuitry and normalized by Automatic Gain Calibration.
2Maximum
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
5
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Signal Processing Characteristics
VOUT(high)
100 90 VOUT (%)
VOUT(%)
tr
tf
100 90
VOUT (V)
10 0 td tf BST
VPROC(high) VPROC VPROC(low) Figure 3. Output Delay Time and Output Fall Time
VOUT(low)
10 0
Figure 2. Output Rise Time and Output Fall Time
Switchpoints VPROC(high) Magnetic Gradient (B) BST BHYS BHYS VPROC VPROC(reduce) VPROC VPROC(high)
Operational Signal Amplitude
Breduce(G)(max) Signal Reduction Breduce(NG)(max) Full Signal Processing Reduced Signal Processing Lowest peak
VPROC(low) 0 Figure 4. Switchpoint and Internal Hysteresis
VPROC(low)
(Baseline)
Figure 5. Maximum Allowable Signal Reduction. Breduce for a given tooth signal is calculated as follows:
Breduce =
Signal Reduction Operational Signal Amplitude
100%
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
6
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Characteristic Performance
Supply Current versus Ambient Temperature 10 9 8 ICC (mA) 7 6 5 4 -50 VCC (V) 3.3 15.0 24 10 16.00
14.00 12.00 10.00
tf (us)
OutputSupply Current versus Supply Voltage Fall Time Versus Ambient Temperature
RPU = 1 k, C L = 4.7 nF
9 8 TA (C) -40 VPU (V) 0 5 25 12 85 150
7 8.00
6.00 6 4.00
5
2.00 0.00 4 0 -50
-25
0
25
50
75 100 TA (C)
125
150
175
-25 5
0
10 25
50 15 75
20 100
125 25 150
30 175
VCC (V) TA (C)
Output Voltage (Low) versus Ambient Temperature 400 350 IOUT (mA) 20 15 10 Edge Position () 300 VOUT(sat) (mV) 250 200 150 100 50 0 -50 -25 0 25 50 75 100 TA (C) 125 150 175 0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3
Relative Timing Accuracy versus Air Gap Falling Mechanical Edge, 1000 rpm, Relative to 0.5 mm Air Gap
TA (C) -40 0 25 85 150
-0.4 0.5
1
1.5
2 AG (mm)
2.5
3
3.5
Relative Timing Accuracy versus Air Gap Rising Mechanical Edge, 1000 rpm, Relative to 0.5 mm Air Gap 0.4 0.3 Edge Position ()
Edge Position ()
Relative Timing Accuracy versus Speed TA = 25C, 1.5 mm Air Gap, Relative to 0.5 mm Air Gap 0.4 0.3 TA (C) -40 0 25 85 150 0.2 0.1 0 -0.1 -0.2 -0.3 Mechanical Edge Falling Rising
0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 0.5 1 1.5 2 AG (mm) 2.5 3 3.5
-0.4 0 500 1000 1500 2000 2500 Gear Speed (rpm)
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
7
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Reference Target 8x
Characteristic
Outside Diameter Face Width Circular Tooth Length Circular Valley Length Tooth Whole Depth Material
Symbol
Do F t tv ht
Test Conditions
Outside diameter of target Breadth of tooth, with respect to sensor Length of tooth, with respect to sensor; measured at Do Length of valley, with respect to sensor; measured at Do
Typ.
120 6 23.6 23.6 5
Units
mm mm mm mm mm -
Symbol Key
Branded Face of Sensor
tV
ODO
F ht
CRS 1018
-
Branded Face of Sensor
Reference Target 8X
Figure 6. Configuration with Reference Target
t
Air Gap
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
8
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Functional Description
Internal Electronics This device contains 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. Sensing Technology The ATS675 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 chopper stabilized Hall element that measures the magnetic gradient created by the passing of a ferrous object. This is illustrated in figure 7. 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. 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 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. Power Supply Protection The ATS675 contains an on-chip regulator and can operate over a wide range of supply voltage levels. For applications using an unregulated power supply, transient protection 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. Output After proper power is applied to the device, it is then capable of providing digital information that is representative of the profile of a rotating gear, as illustrated in figure 8. 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. Output Polarity With the LT device option, the polarity of the output is low when the Hall element is opposite a target tooth, and high when opposite a target valley. The output polarity is opposite in the HT option.. This is illustrated in figure 8. TPOS (True Power-On State) Operation Under specified operating conditions, the ATS675 is guaranteed
Target Mechanical Profile
Tooth Valley |B| BIN
Target (Gear)
Target Magnetic Profile
Low-B field Hall element Leadframe
High-B field Hall IC North Pole Back-Biasing magnet Plastic South Pole Sensor Device
Pole piece (Concentrator)
Sensor Output Electrical Profiles
0 V+ VOUT
LT device option Switch State
V+
On
Off On
Off
On
Off
On
Off
(A)
(B)
HT device option
VOUT
Switch State
Off
On Off On Off
On
Off
On
Figure 7. Application cross-section: (A) target tooth opposite device, and (B) target valley opposite device
Figure 8. Sensor output polarity and switch state (with device connected as shown in figure 1): with LT option, output is low when a target tooth is opposite the Hall element (device on), and high when a target valley is opposite (device off)--polarity response inverts with the HT option.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
9
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
to attain the specified output voltage polarity at power-on, in relation to the target feature nearest the device at that time. The TPOS switchpoint is programmed by Allegro to the datasheet specifications. Start-Up Detection The ATS675 provides an output polarity transition at the first target mechanical edge that is opposite the device after power-on. Calibration The Automatic Gain Calibration (AGC) feature is implemented by a unique patented self-calibrating circuitry. After each poweron, the device measures the peak-to-peak magnetic signal. The gain of the sensor is then adjusted, keeping the internal signal, VPROC , at a constant amplitude throughout the air gap range of the device. This feature ensures that operational characteristics are isolated from the effects of changes in effective air gap. The Initial Calibration process allows the peak detecting DACs to properly acquire the magnetic signal, so that a Running Mode switchpoint can be accurately computed. TPOS to Running Mode After the Initial Calibration process is completed (CALI), the device transitions to Running Mode. As shown in figure 9, the device dynamically adjusts the relative edge position from the TPOS edge location to the Running Mode location over several target teeth (CTPORM), significantly reducing the maximum tim-
ing accuracy step size during startup conditions. A single large jump in edge position is not allowed; instead, any change in edge position from TPOS to Running Mode is spread over several output transitions. Switchpoints The Running Mode switchpoints in the ATS675 are established dynamically as a percentage of the amplitude of the signal, VPROC , after normalization with AGC. Two DACs track the peaks of VPROC. The switching threshold is established at a fixed percentage of the values held in the two DACs. The ATS675 uses a single switching threshold (operate and release points identical) with internal hysteresis. Internal Hysteresis The Internal Hysteresis, BHYS , provides high performance over various air gaps while maintaining immunity to false switching on noise, vibration, backlash, or other transient events. Figure 10 demonstrates the function of this hysteresis when switching on an anomalous peak. Peak and Valley DAC Update The peak and valley DACs have an algorithm that allows tracking of drift over temperature changes, but provides immunity to target particularities, such as small mechanical valleys.
Power-on CALI
CALTPOSRM
Running Mode
BST
BHYS BHYS
VPROC
TPOS Threshold
LT option Switch State VOUT HT option Switch State VOUT
0n 0ff 0ff 0n
LT option Switch State VOUT HT option Switch State VOUT
VPROC
BST
0n 0ff
0ff 0n
Figure 9. Startup calibration order
Figure 10. Output switching can accommodate an anomalous peak, such as the middle peak in this figure, by using the Internal Hysteresis value.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
10
ATS675LSE
Self-Calibrating TPOS Speed 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 11 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 1200
Flux Density, B (G)
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 1000
Flux Density, B (G)
900 800 700 600 500 400 300 200 100 0 0 1.0 2.0 3.0 4.0 5.0 6.0 Tooth Valley
AG (mm)
Figure 11. Magnetic Data for the 8X Reference Target and SE package. Flux density measurements are relative to the baseline magnetic field.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
11
ATS675LSE
Self-Calibrating TPOS Speed Sensor 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, RJA, 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, RJC, is relatively small component of RJA. 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 x IIN T = PD x RJA TJ = TA + T For example, given common conditions such as: TA= 25C, VCC = 12 V, ICC = 7 mA, and RJA = 77 C/W, then: PD = VCC x ICC = 12 V x 7 mA = 84 mW T = PD x RJA = 84 mW x 77 C/W = 6.5C TJ = TA + T = 25C + 6.5C = 31.5C A worst-case estimate, PD(max), represents the maximum allowable power level, without exceeding TJ(max), at a selected RJA and TA. (1) (2) (3) Example: Reliability for VCC at TA = 150C. Observe the worst-case ratings for the device, specifically: RJA = 101 C/W, TJ(max) = 165C, 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) / RJA = 15C / 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 RJA. If VCC(est) VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions.
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
12
ATS675LSE
Self-Calibrating TPOS Speed Sensor Optimized for Automotive Cam Sensing Applications
Package SE 4-Pin SIP Module
1.5
7.00
C
10.00
1.5 3.3
E B
1.3 0.9 4.9 6.2 A 5.7
0.38 24.65 All dimensions nominal, not for tooling use Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown A Dambar removal protrusion (16X) 0.6 2.0
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides) C Active Area Depth, 0.43 mm D Thermoplastic Molded Lead Bar for alignment during shipment E Hall element (not to scale)
11.6
1
2
3
4
A
D
1.6 1.27 5.5 0.7 0.7
Copyright (c)2008, Allegro MicroSystems, Inc. The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com
Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
13


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