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 Supply Voltage VCC Reverse_Supply Voltage VRCC Unit 28 V –18 V ºC TJ(max) 165 ºC Tstg –65 to 170 ºC TA Maximum Junction Temperature Storage Temperature 1 2 3 4 Rating –40 to 150 Operating Ambient Temperature Pin-out Diagram Notes Range L 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 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 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 SROT Reference Target 60-0 0 – 8,000 rpm Analog Signal Bandwidth BW Equivalent to f – 3 dB 20 40 – kHz Operate Point BOP – 120 – mV Release Point BRP – 120 – mV Quantity of rising output (current) edges required for accurate edge detection – – 3 Edge Output switching only; may not meet datasheet specifications – ±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 Rotation Speed 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 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 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 3 Reference Target 60-0 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 (°) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 ATS642LSH Two-Wire True Zero Speed Miniature Differential Peak-Detecting Gear Tooth Sensor with Continuous Calibration 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) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 ATS642LSH Two-Wire True Zero Speed Miniature Differential Peak-Detecting Gear Tooth Sensor with Continuous Calibration 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) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 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 ΔTEAGOUT (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 ΔTEAGIN (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 TEAGOUT = 0.35 mm (shown in panel b), and a decrease of TEAGIN = 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 IN TEAG OUT 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 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* RθJA Package Thermal Resistance Value Units Single-layer PCB with copper limited to solder pads 126 ºC/W Two-layer PCB with 3.8 in.2 of copper area on each side connected with thermal vias and to device ground pin 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) (RθJA = 84 ºC/W) (RθJA = 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 θJ (R θJ 20 40 60 A =1 26 ºC A = /W 84 ºC /W ) ) 80 100 120 Temperature (°C) 140 160 180 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 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 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 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 ECU Short Range for Valid ICC(HIGH) Range for Valid ICC(LOW) Fault ICC(Low)min Open 100 Ω RSENSE Figure 7: Typical Application Circuit 0 Figure 8: Diagnostic Characteristics of Supply Current Values Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 ATS642LSH Two-Wire True Zero Speed Miniature Differential Peak-Detecting Gear Tooth Sensor with Continuous Calibration 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 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, 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 × IIN T = PD × RJA TJ = TA + ΔT (1) (2) 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: RJA = 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: Tmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C This provides the allowable increase to TJ resulting from internal power dissipation. Then, invert equation 2: PD(max) = Tmax ÷ RJA = 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 RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions. (3) For example, given common conditions such as: TA= 25°C, VCC = 12 V, ICC = 4 mA, and RJA = 140 °C/W, then: PD = VCC × ICC = 12 V × 4 mA = 48 mW T = PD × RJA = 48 mW × 140 °C/W = 7°C TJ = TA + T = 25°C + 7°C = 32°C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RJA and TA. Allegro MicroSystems, Inc. 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, Inc. 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 ©2004-2009, 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 16