ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Features and Benefits Description ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ Recognizing the increasingly stringent requirements for EMC/ EMI in automotive applications, Allegro has taken the necessary steps to design devices that are capable of withstanding the effects of radiated and conducted transients. The ATS673 and ATS674 devices have been designed specifically for this purpose. Advanced circuitry on the die allows them to survive positive and negative transient pulses on both the input and output. Tight timing accuracy over operating temperature range True zero-speed operation TPOS (True Power-On State) Air-gap-independent switchpoints High immunity to vibration Large operating air gaps Operation with supply voltages down to 3.3 V Digital output representing target profile Single-chip solution for high reliability Optimized Hall IC/magnet system The ATS673 and ATS674 devices retain all of the same characteristics as the ATS671 and ATS672. The devices remain true zero-speed gear tooth sensors with optimized Hall IC/ magnet configuration in an SIP (single in-line package). The SIP assembly consists of a molded package that holds together a samarium cobalt magnet, a pole piece, and a true zero-speed Hall IC that has been optimized to the magnetic circuit. Continued on the next page… Packages: 4 pin SIP (suffix SE) The sensor incorporates a single element Hall IC that switches in response to magnetic signals created by a ferrous target. The IC contains a sophisticated digital circuit designed to eliminate the detrimental effects of magnet and system offsets. Signal processing is used to provide zero-speed Continued on the next page… Not to scale Functional Block Diagram V+ VCC Voltage Regulator (Analog) Voltage Regulator (Digital) VREG(A) Hall Amp VREG(D) Automatic Gain Control Offset Adjust Temperature Coefficient Adjust Offset LPF TC VPROC VREF 9-Bit PDAC 9 Comp_P Clock Continuous Update Logic 0.1 μF CBYPASS 9-Bit Counter Threshold Output Output State Clock Continuous Update Logic Comp_N Output State 9-Bit Counter 9 9-Bit NDAC TPOS VREG(A) VREG(D) Power-On Reset Output Driver Threshold Comparator TPOS Trim GND TEST (Recommended) ATS673-DS, Rev. 1 VOUT Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Features and Benefits (continued) ▪ AGC and reference adjust circuit ▪ Undervoltage lockout Description (continued) performance independent of air gap and also to dynamically adapt device performance to the typical operating conditions found in automotive applications, particularly cam sensing applications (reduced vibration sensitivity). High-resolution (9-bit) peak detecting DACs are used to set the adaptive switching thresholds of the devices, ensuring high accuracy even in the presence of gear eccentricity. Hysteresis in the thresholds reduces the negative effects of anomalies in the magnetic signal (such as magnetic overshoot) associated with the targets used in many automotive applications. The ATS673 and 674 also include a low bandwidth filter that increases the noise immunity and the signal to noise ratio of the sensor. Two options are available for output polarity, low over tooth (LT) and high over tooth (HT). For applications requiring absolute accuracy use the ATS674. The ATS673 should be used for targets with high wobble. Selection Guide Part Number Pb-free1 ATS673LSETN-LT-T Yes Low ATS673LSETN-HT-T Yes High ATS674LSETN-LT-T Yes Low ATS674LSETN-HT-T Yes High VOUT (Over Tooth) Packing2 Application High target wobble 13-in. reel, 450 pieces/reel High absolute edge detection accuracy 1Pb-based variants are being phased out of the product line. Certain variants cited in this footnote are in production but have been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006. These variants include: ATS673LSETN-LT, ATS673LSETN-HT, ATS674LSETN-LT, and ATS674LSETN-HT. 2Contact Allegro for additional packing options. Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Supply Voltage VCC 28 V Reverse-Supply Voltage VRCC –18 V Continuous Output Current IOUT 20 mA Reverse Output Current IROUT 50 mA –40 to 150 ºC Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) 165 ºC Tstg –65 to 170 ºC Storage Temperature Pin-out Diagram Range L Terminal List Name VCC 1 2 3 4 Description Number Connects power supply to chip 1 VOUT Device output 2 TEST For Allegro use, float or tie to GND 3 GND Ground terminal 4 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 2 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 OPERATING CHARACTERISTICS Valid at TA = –40°C to 150°C, TJ ≤ TJ(max), over full range of AG, unless otherwise noted Characteristic Min. Typ.1 Max. Units Operating; TJ < TJ(Max) 3.3 – 26.5 V Symbol Test Conditions ELECTRICAL CHARACTERISTICS Supply Voltage VCC – – <VCC(Min) V Supply Zener Clamp Voltage VZSupply ICC = ICC(Max) + 3 mA, TA = 25°C 28 31 35 V Supply Zener Current2 IZSupply Undervoltage Lockout VCCUV VSupply = 27 V – – 14 mA Supply Current ICC Output = OFF or ON 3 6.5 11 mA Reverse Supply Current IRCC VRCC = –18 V – –5 –10 mA tPO Gear Speed < 100 rpm; VCC > VCC(Min) – – 500 μs ISINK = 15 mA, Output = ON – 200 450 mV POWER-ON CHARACTERISTICS Power-On Time3 OUTPUT CHARACTERISTICS Low Output Voltage VOUT(Sat) Output Zener Voltage VZOUT IOUT = 3 mA, TA = 25°C 30 – – V Output Current Limit IOUTLIM Output = ON, VOUT = 12 V 35 57 90 mA Output Leakage Current IOUTOFF Output = OFF, VOUT = VCC(Max) – – 10 μA Output Rise Time tr 10/90% points; RLOAD = 500 Ω, CLOAD = 10 pF, TA = 25°C – 0.9 5 μs Output Fall Time tf 10/90% points; RLOAD = 500 Ω, CLOAD = 10 pF, TA = 25°C Over tooth HT device option Over valley – – 0.5 HIGH 5 – μs V V Output Polarity VOUT LT device option – LOW – Over tooth – LOW – V Over valley – HIGH – V Continued on the next page... V+ Output Rise and Fall Time VOUT(High) % 100 90 10 0 VOUT(Low) t+ tr tf Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 3 ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications OPERATING CHARACTERISTICS, continued Valid at TA = –40°C to 150°C, TJ ≤TJ(max), over full range of AG, unless otherwise noted Characteristic Symbol Test Conditions Min. Typ.1 Max. Units SWITCHPOINT CHARACTERISTICS Tooth Speed Tooth frequency, target generating sinusoidal signal 0 – 8 kHz BW Corresponds to output switching frequency – 3 dB – 40 – kHz Operate BOP ATS673 % of peak-to-peak, referenced to tooth signal, ATS674 AG < AG(Max) – 40 – % – 30 – % Release BRP ATS673 % of peak-to-peak, referenced to tooth signal, ATS674 AG < AG(Max) – 50 – % – 40 – % Quantity of rising edges required to complete edge detection calibration – – 3 edges Bandwidth S CALIBRATION CHARACTERISTICS4 Initial Calibration CalIC AGC Disable CalAGC Quantity of rising edges required to complete Automatic Gain Control calibration – – 3 edges Calibration Update CalUPD Quantity of rising edges required to update edge detection calibration while running after initial calibration – Continuous – edges PERFORMANCE CHARACTERISTICS3 TPOS Air Gap Range5 Operational Air Gap Range AGTPOS AG TPOS functionality guaranteed 0.5 – 2.5 mm TPOS guaranteed, output switching, running mode 0.5 – 2.5 mm Extended Minimum Air Gap6 AGEXTMIN Output switching, running mode; valleys may be detected as teeth in this range – – 0.5 mm Extended Maximum Air Gap7 AGEXTMAX Output switching, running mode; teeth may be detected as valleys in this range 2.5 – 5 mm – 3 6 deg – 3 6 deg Relative Timing Accuracy4,8 Phase Delay9 1Typical ErrICREL ATS673 During initial calibration; rising or falling edges, gear speed = 1000 rpm, target eccentricity ATS674 < 0.1 mm ErrRELR ATS673 Rising edges; after initial calibration, gear speed ATS674 = 1000 rpm, target eccentricity < 0.1 mm – 0.5 0.8 deg – 0.4 0.8 deg ErrRELF ATS673 Falling edges; after initial calibration, gear speed ATS674 = 1000 rpm, target eccentricity < 0.1 mm – 0.8 1.2 deg – 0.6 1.2 deg After initial calibration, AG = 1.5 mm, TA = 25°C – 1.6 x 10–4 – deg/rpm ΔErrSREL values are taken at VCC = 12 V and TA = 2I ZSupply(Max) is equivalent to ICCON(Max) + 3 mA. 3Using reference target 8X. 25°C. 4The term edge refers to a mechanical edge, such as the side of a gear tooth, passing under the device. Rising edge: from valley to approaching tooth. Falling edge: from tooth to approaching valley. 5The TPOS Air Gap Range is the range of installation air gaps within which the TPOS (True Power-On State) function is guaranteed to correctly detect a tooth when powered-on over a tooth and correctly detecting a valley when powered-on over a valley, using reference target 8X or equivalent, as specified in the Target/Gear Parameters for Correct TPOS Operation section in this document. 6The Extended Minimum Air Gap is a range of installation air gaps, smaller than AG (Min), within which the the device will accurately detect target features but TPOS is NOT guaranteed to be fully accurate, possibly evaluating the initial valley as a tooth. 7The Extended Maximum Air Gap is an extended range of installation air gaps, greater than AG (Max), within which the the device will accurately detect target features but TPOS is not guaranteed to be fully accurate, possibly evaluating the intiial tooth as a valley. 8Relative Timing Accuracy is the change in edge position before the resulting change in device output; for a single device, over the full Operational Air Gap Range, AG, and Operating Ambient Temperature, TA , range. 9Phase Delay is the change in edge position at detection, through the full operational Tooth Speed, S, range for a single device, and at a single ambient temperature, TA, and installation air gap, AG. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 4 ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Air Gap Comparisons Target (Gear) Extended Maximum Air Gap, AGEXTMAX Installation Air Gap 9 Operational Air Gap Range, AG TPOS Air Gap Range, AGTPOS Extended Minimum Air Gap Air Gap, AGEXTMIN Sensor Device Branded Face Relative Timing Accuracy Target Mechanical Profile V+ Sensor Output Electrical Profile -HT Option VOUT t ErrRELR(Max – Min) ErrRELF(Max – Min) Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 5 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Reference Target (Gear) Information REFERENCE TARGET 8X Symbol Test Conditions Typ. Units 120 mm Do Outside diameter of target Face Width F Breadth of tooth, with respect to sensor 6 mm Circular Tooth Length t Length of tooth, with respect to sensor; measured at Do 23.6 mm Circular Valley Length tv Length of valley, with respect to sensor; measured at Do 23.6 mm Tooth Whole Depth ht 5 mm – – Outside Diameter Material CRS 1018 Symbol Key Branded Face of Sensor tV t Characteristic ØDO F ht Air Gap Branded Face of Sensor Reference Target 8X Figure 1. Configuration with Reference Target Target/Gear Parameters for Correct TPOS Operation For TPOS to function as specified, the target must generate a minimum of 120 G difference between the magnetic field over a tooth and the field over a valley, at the maximum installation air gap. A target complying with the material and dimensions cited for the reference target 8X, generates the required 120 G differential. The following recommendations should be followed in the design and specification of targets: • Tooth width, t ≥ 5 mm • Valley width, tv > 13 mm • Valley depth, ht > 5 mm • Tooth thickness, F ≥ 5 mm Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 6 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Characteristic Data: Electrical Supply Current (On) Versus Ambient Temperature Supply Current (Off) Versus Ambient Temperature 11 10 10 ICC(ON) (mA) 9 VCC (V) 8 26.5 15.0 3.3 7 6 ICC(OFF) (mA) 11 9 VCC (V) 26.5 15.0 3.3 8 7 6 5 5 4 4 3 3 -50 -25 0 25 50 75 100 125 150 175 -50 -25 0 25 Supply Current (On) Versus Supply Voltage 100 125 150 175 Supply Current (Off) Versus Supply Voltage 11 11 10 10 9 9 TA (°C) 8 -40 0 25 85 150 7 6 5 ICC(OFF) (mA) ICC(ON) (mA) 75 TA (°C) TA (°C) TA (°C) 8 -40 0 25 85 150 7 6 5 4 4 3 3 0 5 10 15 20 25 30 0 5 10 Output Voltage (Low) Versus Ambient Temperature 20 25 30 Output Leakage Current (Off) Versus Ambient Temperature 500 10 400 200 100 IOUT(OFF) (uA) 8 IOUT (mA) 20 15 10 300 6 4 2 0 -50 15 VCC (V) VCC (V) VOUT(SAT) (mV) 50 0 -25 0 25 50 75 TA (°C) 100 125 150 175 -50 -25 0 25 50 75 100 125 150 175 TA (°C) Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 7 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Characteristic Data: Relative Timing Accuracy ATS673 Relative Timing Accuracy Versus Air Gap ATS673 Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge Falling Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 1000 rpm, Relative to 0.5 mm Air Gap 1.2 0.0 1.0 -0.2 TA (°C) -0.3 –40 0 25 85 150 -0.4 -0.5 -0.6 Edge Position (°) Edge Position (°) -0.1 -0.7 -0.8 TA (°C) 0.8 –40 0 25 85 150 0.6 0.4 0.2 0.0 0.5 1.0 1.5 2.0 2.5 0.5 3.0 1.0 AG (mm) 2.0 2.5 3.0 AG (mm) ATS674 Relative Timing Accuracy Versus Air Gap ATS674 Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge Falling Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 1000 rpm, Relative to 0.5 mm Air Gap 0.0 1.2 -0.1 1.0 -0.2 TA (°C) -0.3 –40 0 25 85 150 -0.4 -0.5 -0.6 Edge Position (°) Edge Position (°) 1.5 TA (°C) 0.8 –40 0 25 85 150 0.6 0.4 0.2 -0.7 -0.8 0.0 0.5 1.0 1.5 2.0 2.5 0.5 3.0 1.0 AG (mm) 2.0 2.5 3.0 AG (mm) Relative Timing Accuracy Versus Air Gap Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge Falling Mechanical Edge 1.5 mm Air Gap, Relative to 0.5 mm Air Gap 1.5 mm Air Gap, Relative to 0.5 mm Air Gap 0.40 0.40 0.30 0.30 0.20 0.10 ATS673 ATS674 0 -0.10 -0.20 -0.30 Edge Position (°) Edge Position (°) 1.5 0.20 0.10 ATS673 ATS674 0 -0.10 -0.20 -0.30 -0.40 -0.40 0 500 1000 1500 Gear Speed (rpm) 2000 2500 0 500 1000 1500 2000 2500 Gear Speed (rpm) Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 8 ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Operational Description is illustrated in figure 2. The difference in the magnetic gradients created by teeth and valleys allows the devices to generate a digital output signal. Assembly Description The ATS673 and ATS674 true zero-speed gear tooth sensors have a Hall IC-magnet configuration that is fully optimized to provide digital detection of gear tooth edges. This sensor is integrally molded into a plastic body that has been optimized for size, ease of assembly, and manufacturability. High operating temperature materials are used in all aspects of construction. Output After proper power is applied to the devices, they are then capable of providing digital information that is representative of the profile of a rotating gear, as illustrated in figure 3. No additional optimization is needed and minimal processing circuitry is required. This ease of use reduces design time and incremental assembly costs for most applications. Sensing Technology The gear tooth sensor contains a single-chip Hall effect sensor IC, a 4-pin leadframe and a specially designed rare-earth magnet. The Hall IC supports a Hall element that measures the magnetic gradient created by the passing of a ferrous object. This Target (Gear) Low-B field Hall element Leadframe High-B field Hall IC North Pole Sensor Device Back-Biasing magnet Plastic Pole piece (Concentrator) South Pole (A) (B) Figure 2. Device Cross Section. Motion of the target is detected by the Hall element mounted on the Hall IC. Panel A, the presence of a tooth feature on the target is distinguished by a high magnetic flux density, B. Panel B, the presence of a valley feature is distinguished by its low magnetic flux density. Target Mechanical Profile Target Magnetic Profile -LT Option Sensor Output Switch State Sensor Output Electrical Profile -HT Option Sensor Output Switch State Sensor Output Electrical Profile B BIN 0 On Off On Off On Off On Off Off On Off On Off On Off On V+ VOUT V+ VOUT Figure 3. The magnetic profile reflects the geometry of the target, allowing the device to present an accurate digital output response. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 9 ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Power Supply Protection The ATS673 and ATS674 contain an on-chip regulator and can operate over a wide range of supply voltage levels. For applications using an unregulated power supply, transient protection must be added externally. For applications using a regulated supply line, EMI and RFI protection may still be required. The circuit shown in figure 5 is the basic configuration required for proper device operation. Contact Allegro field applications engineering for information on the circuitry required for compliance to various EMC specifications. TPOS (True Power-On State) Operation Under specified operating conditions, the devices are guaranteed to attain a specified output voltage polarity at power-on, in relation to the target feature nearest the device at that time. Both devices offer the options of either high or low polarity over initial tooth or valley. This polarity also applies throughout device operation. Start-Up Detection These devices provide an output polarity transition at the first mechanical edge after power-on. Internal Electronics These devices contain a self-calibrating Hall effect IC that provides a Hall element, a temperature compensated amplifier, and offset cancellation circuitry. The IC also contains a voltage regulator that provides supply noise rejection over the operating voltage range. The Hall transducers and the electronics are integrated on the same silicon substrate by a proprietary BiCMOS process. Changes in temperature do not greatly affect this device due to the stable amplifier design and the offset rejection circuitry. Undervoltage Lockout When the supply voltage falls below the undervoltage lockout level, VCCUV, the device switches to the OFF state. The device remains in that state until the voltage level is restored to to the VCC operating range. Changes in the target magnetic profile have no effect until voltage is restored. This prevents false signals caused by undervoltage conditions from propagating to the output of the sensor. VS 1 VCC CBYPASS 0.1 μF 3 RPU ATS673/674 TEST VOUT 2 Sensor Output GND 4 Figure 5. Power Supply Protection Typical Circuit 10 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 adjusted, keeping the internal signal amplitude constant over the air gap range of the device. This feature ensures that operational characteristics are isolated from the effects of changes in AG. The effect of AGC is shown in figure 7. AGC (Automatic Gain Control) The AGC feature is implemented by a unique patented selfcalibrating circuitry. After each power-on, the devices measure the peak-to-peak magnetic signal. The gain of the sensor is then Magnetic Flux Density Versus Target Edge Position 600 AG (mm): Flux Density, B (G) 500 1.50 2.00 400 2.50 300 3.00 3.50 200 100 0 0 10 20 30 40 50 60 70 80 90 Target Rotation (°) Internal Analog Signal after AGC Versus Target Edge Position 2.0 AG (mm): 1.50 2.00 2.50 3.00 3.50 VPROC (V) 1.5 1.0 0.5 0 0 10 20 30 40 50 60 70 80 90 Target Rotation (°) Figure 7. Effect of AGC. The upper panel shows the magnetic gradient detected at the Hall element, with no amplification. The lower panel displays the corresponding internal processed signal, VPROC. This normalized electrical signal allows optimal performance by the rest of the circuits that reference this signal. 11 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Switchpoints Switchpoints in the ATS673 and ATS674 are established dynamically as a percentage of the amplitude of the signal, VPROC, after normalization with AGC. Two DACs track the peaks of VPROC (see the Update subsection). The switching thresholds are established at fixed percentages of the values held in the two DACs. The value of the thresholds has been carefully selected, where the signal is steepest and least affected by air gap variation, thus providing the most accurate and consistent switching. The low hysteresis, 10%, provides high performance over various air gaps while maintaining immunity to false switching on noise, vibration, backlash, or other transient events. Figure 8 graphically demonstrates the establishment of the switching threshold levels. Because the thresholds are established dynamically as a percentage of the peak-to-peak signal, the effect of a baseline shift is minimized. Target Mechanical Profile V+ 100 BRP% BOP% VPROC (%) ATS673 and ATS674 0 Device State -LT option -HT option On Off On Off Off On Off On Figure 8. Switchpoint Relationship to Thresholds.The device switches when VPROC passes a threshold level, BOP or BRP , while changing in the corresponding direction: increasing for a BOP switchpoint, and decreasing for a BRP switchpoint. 12 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Update in real time, the sensor has high immunity to target run-out and retains excellent accuracy and functionality in the presence of both run-out and transient mechanical events. Figure 9 shows how the devices use historical data to provide the switching thresholds for a given edge. The ATS673 and ATS674 incorporate an algorithm that continuously monitors the system and updates the switching thresholds accordingly. The switchpoint for each transition is determined by the previous two transitions. Because variations are tracked (A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift (B) Internal analog signal, VPROC, typically resulting in the sensor V+ Smaller TEAG Smaller TEAG Target Sensor VPROC (V) Larger TEAG Target Smaller TEAG Hysteresis Band (Delimited by switchpoints) Larger TEAG Sensor 360 0 Target Rotation (°) (C) Referencing the internal analog signal, VPROC, to continuously update device response Determinant Peak Values BOP1 BRP1 Pk1, Pk2 Pk2, Pk3 BOP2 BRP2 Pk3, Pk4 Pk4, Pk5 BOP3 BRP3 Pk5, Pk6 Pk6, Pk7 BOP4 Pk7, Pk8 BRP4 Pk8, Pk9 V+ BHYS Pk1 BHYS BHYS Pk9 BHYS Pk7 Pk3 Pk5 VPROC (V Switchpoint BOP1 BOP2 BOP3 BRP1 BOP4 BRP3 BRP4 BRP2 Pk4 Pk6 Pk2 Pk8 BHYS BHYS BHYS BHYS t+ Figure 9. The Continuous Update algorithm allows the Allegro sensor to immediately interpret and adapt to significant variances in the magnetic field generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently update the device switchpoints (BOP and BRP). The hysteresis, BHYS(#x), at each target feature configuration results from this recalibration, ensuring that it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC. As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the sensor as a varying magnetic field, which results in proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish accurate switchpoints based on the fluctuation of VPROC, as shown in panel C. 13 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Sensor and Target Evaluation Magnetic Profile In order to establish the proper operating specification for a particular sensor device and target system, a systematic evaluation of the magnetic circuit should be performed. The first step is the generation of a magnetic map of the target. By using a calibrated device, a magnetic profile of the system is made. Figure 10 is a magnetic map of the 8X reference target. A pair of curves can be derived from this map data, and be used to describe the tooth and valley magnetic field strength, B, versus the size of the air gap, AG. This allows determination of the minimum amount of magnetic flux density that guarantees operation of the sensor, so the system designer can determine the maximum allowable AG for the sensor and target system. One can also determine the TPOS air gap capabilities of the sensor by comparing the minimum tooth signal to the maximum valley signal. Magnetic Map, Reference Target 8X with SE Package 1600 1400 Flux Density, B (G) 1200 1000 800 600 400 200 0 0 60 120 180 240 300 360 Target Rotation (°) Air Gap Versus Magnetic Field, Reference Target 8X with SE Package 1300 1200 1100 Flux Density, B (G) 1000 900 800 700 600 500 Tooth 400 Valley 300 200 100 0 0 1.0 2.0 3.0 4.0 5.0 6.0 AG (mm) Figure 10. Magnetic Data for the 8X Reference Target and SE package. 14 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Accuracy While the update algorithm will allow the sensor devices to adapt to typical air gap variations, major changes in air gap can adversely affect switching performance. When characterizing sensor performance over a significant air gap range, be sure to repower the device at each test at different air gaps. This ensures that self-calibration occurs for each installation condition. See the Operating Characteristics table and the charts in the Characteristic Data: Relative Timing Accuracy section for performance information. Sensor Evaluation: EMC Characterization Only Test Name* Reference Specification ESD – Human Body Model ESD – Machine Model Conducted Transients Direct RF Injection Bulk Current Injection TEM Cell *Please contact Allegro for EMC performance AEC-Q100-002 AEC-Q100-003 ISO 7637-1 ISO 11452-7 ISO 11452-4 ISO 11452-3 Related Documents Documents that can be found on the Allegros web site,: www.allegromicro.com: • Definition of Terms (Pub 26004) • Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and Lead forming (AN27703.1) • Storage of Semiconductor Devices (Pub 26011) • Hall Effect Applications Guide (Pub 27701) • Applications Note: Back-Biased Packaging Advances (SE, SG & SH versus SA & SB) 15 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Power Derating THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions* RθJA Package Thermal Resistance Value Units 1-layer PCB with copper limited to solder pads 101 ºC/W 1-layer PCB with copper limited to solder pads and 3.57 in.2 (23.03 cm2) of copper area each side 77 ºC/W *Additional information is available on the Allegro Web site. Power Derating Curve 30 VCC(max) Maximum Allowable VCC (V) 25 20 1-Layer PCB (RθJA = 77 ºC/W) 15 Pads Only PCB (RθJA = 101 ºC/W) 10 5 VCC(min) 0 20 40 60 80 100 120 140 160 180 Power Dissipation, PD (m W) Power Dissipation Versus Ambient for Sample PCBs 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 L (R owK θJ A = PC 77 B ºC /W Mi (R nim um θJ A = 10 K P 1 º CB C/ W ) 20 40 60 ) 80 100 120 140 Temperature, TA (°C) 160 180 16 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications The device must be operated below the maximum junction temperature of the device, TJ(max). Under certain combinations of peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the application. This section presents a procedure for correlating factors affecting operating TJ. (Thermal data is also available on the Allegro MicroSystems Web site.) The Package Thermal Resistance, RθJA, is a figure of merit summarizing the ability of the application and the device to dissipate heat from the junction (die), through all paths to the ambient air. Its primary component is the Effective Thermal Conductivity, K, of the printed circuit board, including adjacent devices and traces. Radiation from the die through the device case, RθJC, is relatively small component of RθJA. Ambient air temperature, TA, and air motion are significant external factors, damped by overmolding. The effect of varying power levels (Power Dissipation, PD), can be estimated. The following formulas represent the fundamental relationships used to estimate TJ, at PD. PD = VIN × IIN (1) ΔT = PD × RθJA (2) TJ = TA + ΔT (3) Example: Reliability for VCC at TA = 150°C, package SE, using minimum-K PCB. Observe the worst-case ratings for the device, specifically: RθJA = 101°C/W, TJ(max) = 165°C, VCC(max) = 26.5 V, and ICC(max) = 11 mA. Note that ICC(max) at TA = 150°C is lower than the ICC(max) at TA = 25°C given in the Operating Characteristics table. Calculate the maximum allowable power level, PD(max). First, invert equation 3: ΔTmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C This provides the allowable increase to TJ resulting from internal power dissipation. Then, invert equation 2: PD(max) = ΔTmax ÷ RθJA = 15°C ÷ 101 °C/W = 91 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 91 mW ÷ 11 mA = 8.3 V The result indicates that, at TA, the application and device can dissipate adequate amounts of heat at voltages ≤VCC(est). Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions. For example, given common conditions such as: TA= 25°C, VIN = 12 V, IIN = 4 mA, and RθJA = 140 °C/W, then: PD = VIN × IIN = 12 V × 4 mA = 48 mW ΔT = PD × RθJA = 48 mW × 140 °C/W = 7°C TJ = TA + ΔT = 25°C + 7°C = 32°C A worst-case estimate, PD(max), represents the maximum allowable power level, without exceeding TJ(max), at a selected RθJA and TA. 17 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications ATS673 and ATS674 Package SE, 4-Pin SIP 7 .276 10 C .394 B 3.3 .130 E 6.2 .244 4.9 .193 1.3 0.38 .015 A .051 1.08 .043 20.95 .825 11.6 .457 1 2 3 4 A D 0.6 .240 1.27 .050 2 .079 Preliminary dimensions, for reference only Untoleranced dimensions are nominal. Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only Dimensions exclusive of mold flash, burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Dambar removal protrusion (16X) B Metallic protrusion, electrically connected to pin 4 and substrate (both sides) C Active Area Depth, 0.43 mm [.017] D Thermoplastic Molded Lead Bar for alignment during shipment E Hall element (not to scale) 18 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com ATS673 and ATS674 Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; 6,297,627; 6,525,531; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. Copyright © 2005, 2006 Allegro MicroSystems, Inc. 19 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com