ATS672LSB_03 ALLEGRO | Alldatasheet
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NOTE: For detailed information on purchasing options, contact your local Allegro field applications engineer or sales representative. Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use. Recommended Substitutions: Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Date of status change: May 1, 2006 These parts are no longer in production The device should not be purchased for new design applications. Samples are no longer available. Discontinued Product
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com Allegro MicroSystems, Inc. 1234 1. VCC 2. VOUT 3. Test pin (tie to GND) 4. GND AB SO LUTE MAX I MUM RAT INGS Operating Temperature Ambient, T
- Tight timing accuracy throughout temperature range
- True zero-speed operation
- Air gap-independent switch points
- Large operating air gaps
- Operation down to 3.3 V
- Digital output representing target profi les The ATS672 true zero-speed gear tooth sensors provide manufacturer-friendly solutions for digital gear tooth sensing applications, through an optimized con- fi guration of Hall-effect IC and magnet, packaged together in a single SIP (Single In Line Package) module. The SIP consists of an overmolded enclosure, which encapsulates a samarium cobalt magnet, a pole piece, and a true zero-speed Hall- effect IC that has been optimized to the magnetic circuit. This package can be easily assembled and used in conjunction with gears of various shapes and sizes. The ATS672 sensor incorporates a single-element Hall-effect IC that switches in response to the magnetic signal created by a ferrous target (the gear). The IC con- tains a sophisticated digital circuit designed to eliminate the detrimental effects of magnet and system offsets. Signal processing is used to provide zero-speed perfor- mance, independent of air gap, and also to dynamically adapt device performance to the typical operating conditions found in automotive applications, such as reducing sensitivity to vibration. High resolution (9 bit) peak-detecting DACs are used to set the adaptive switching thresholds of the device. Hysteresis in the thresholds reduces the negative effects of any anomalies in the magnetic signal (such as magnetic overshoot) associated with the targets used in many automotive applications. The ATS672 also includes a low-bandwidth fi lter that increases the noise immunity and the signal-to-noise ratio of the sensor. These features result in potential improve- ments in both the timing accuracy and the jitter performance of the device. The ATS672LSB version is optimized for gear tooth sensing applications. The ATS672LSB-LT is optimized for cam sensing. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture Use the following complete part numbers when ordering: Part Number Package Application ATS672LSB 4-pin plastic SIP Gear tooth sensing ATS672LSB-LT 4-pin plastic SIP Cam sensing Package SB, 4-pin SIP Features and Benefi ts
- Single-chip solution for high reliability
- Small mechanical dimensions
- Optimized Hall-effect IC/magnetic systems
- AGC and reference-adjust circuits
- Undervoltage lockout
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Functional Block Diagram Output Driver Amp Regulator (Digital) GND VOUT VCC Dynamic Offset Cancellation TC Adjust Regulator (Analog) Threshold Comparator Test VREF Low Pass Filter Power On Reset Automatic Gain Control (Analog) VTHRESH Offset TC
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB OPERATING CHARACTERISTICS Valid at Ta = –40ºC to 150ºC, and VCC within specifi cation, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Units
Electrical Characteristics
CC Operating; TJ < TJ(max) 3.3 – 26.5 V Reverse Supply Voltage V RCC IRCC = –5 mA, maximum – – –18 V Supply Zener Clamp Voltage V ZSupply ICC = 14 mA (≈ICC(max) + 3 mA); TA = 25°C 28 – – V Output Zener Clamp Voltage V ZOutput IOUT = 3 mA; TA = 25°C 30 – – V Supply Zener Current I ZSupply Test conditions only; VCC = 28 V – – I CC(max) + 3 mA Output Zener Current I ZOutput VOUT = 30 V – – 3 mA Supply Current I CC Output = OFF 3 6.5 11 mA Output = ON 3 6.5 11 mA Power-On State Characteristics Power-On Time t PO Gear Speed < 100 RPM; VCC > 3.3 V – – 500 µs Undervoltage Lockout V UV – – < V CC(min) V Output Stage Low Output Voltage V LOUT ISINK = 15 mA, Output = ON – 0.2 0.45 V Output Current Limit I lim Output = ON; TJ < TJ(max) 25 45 70 mA Output Leakage Current I OFF Output = OFF; VOUT = VCC(max) – – 10 µA Output Rise Time t r RLOAD = 500 Ω; CLOAD = 10 pF; TA = 25°C – 0.9 5 µs Output Fall Time t f RLOAD = 500 Ω; CLOAD = 10 pF; TA = 25°C – 0.5 5 µs Switch Point Characteristics Tooth Speed S max 0 – 8 kHz Bandwidth f – 3 dB – 40 – kHz Operate Point B OP % of peak-to-peak, referenced to tooth sensing signal; AG < AGMax –3 0 – % Release Point B RP % of peak-to-peak, referenced to tooth sensing signal; AG < AGMax –4 0 – % Output Polarity V OUT Valley opposite the sensor – HIGH – Tooth opposite the sensor – LOW – Calibration Initial Calibration C I Number of rising mechanical edges on the target that are required for accurate edge detection –2 3 AGC Disable C f Number of rising mechanical edges on the target that are required to complete the AGC calibration –– 3
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Output Rise Time (tr) and Fall Time (tf) 100% Output High Output Low 90% 10% t (s) tr tf VOUT (V) t( µs) Output Voltage Rise Duration RLOAD = 500Ω,C LOAD =1 0p F VOUT (V) 0.00 2.00 4.00 8.00 10.00 6.00 t( µs) VOUT (V) Output Voltage Fall Duration RLOAD = 500Ω,C LOAD =1 0p F 0.00 2.00 4.00 8.00 10.00 6.00 5.0
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB OPERATING CHARACTERISTICS using reference target 8X and test circuit #1; air gap within AG range, and over rated ambient temperature range, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Units Relative Timing Accuracy* TICRel During initial calibration; rising and falling mechanical edges; RPM = 1000; gear eccentricity < 0.1 mm – 3 6 deg. TRel After initial calibration; rising mechanical edge; RPM = 1000; gear eccentricity < 0.1 mm – 0.3 0.6 deg. After initial calibration; falling mechanical edge; RPM = 1000; gear eccentricity < 0.1 mm – 0.5 0.8 deg. Operational Air Gap Range AG Output switching: Running mode only – 0.5 2.5 mm *Relative Timing Accuracy range is the change in edge position over the AG range and the device operating temperature range. ICC On, VCC =4 . 0V -40 25 150 ICC (mA) ICC Off, VCC =4 . 0V -40 25 150 ICC (mA) 150 225 300 375 450 -40 25 150 TA (°C) VSAT (mV) TA (°C) TA (°C) VSAT at ISINK = 15 mA, VCC = 4.0 V
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB POR. (Power-On Reset) Allows complete reset to the original power-on state, when initial calibration occured, regardless of the state of the device immediately prior to POR. TC. (Temperature Coeffi cient) This supports fi ne tuning of the ATS672 for fl at parametric performance over the full rated oper- ating temperature range. Sensor Integration. The ATS672 contains a self-calibrating Hall-effect IC that possesses temperature compensated amplifi er circuitry and a voltage regulator that provides supply noise rejec- tion over the operating voltage range. The Hall transducer and the electronics are integrated on the same silicon substrate using a proprietary BiCMOS process. Changes in temperature do not greatly affect this device due to the stable amplifi er design and the offset rejection circuitry. Assembly Description. The ATS672 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. Operation. When proper power is applied to the sensor, it is capable of providing digital information that is representative of the profi le of a rotating gear. No additional optimization is needed and minimal processing circuitry is required. This ease of use should reduce design time and incremental assembly costs for most applications. Sensing Technology. The sensor contains a single-chip Hall- effect sensor IC, a 4-pin leadframe, and a specially-designed rare earth magnet. The Hall IC possesses a Hall element that mea- sures the magnetic gradient created by the passing of a ferrous object. The difference in the magnetic gradients created by a tooth and valley allow the generation of the digital output signal. The following output diagram corresponds to a sensor with the standard polarity. Functional Description Sensing technology. As the target moves by the sensor, there is a change in the magnetic fl ux density, B, which is measured in gauss (G). The left panel shows the effect of a tooth opposite the sensor, a higher B. The right panel shows the effect of a valley, a lower B. Ferrous Target Magnetic Gradient Digital Output Signal Mechanical Profile
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Start-Up Detection. The ATS672 generates a digital output transition when the fi rst rising or falling mechanical edge is detected after being powered-on, indicating when the fi rst sig- nifi cant motion in the target is detected. Undervoltage Lockout. When the supply voltage falls below the minimum operating voltage, VCCUV, the device turns off. It then stays off, regardless of the state of the magnetic fi eld, until an operating range VCC is restored. It then turns on again. This lockout feature prevents false signals, caused by undervoltage conditions, from propagating to the output of the sensor. Power Supply Protection. The device contains an on-chip regulator and can operate over a wide V CC 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 specifi cations. Automatic Gain Control (AGC). The patented self-calibrat- ing circuitry is unique. Each time the device is powered-on, the device starts measuring the peak-to-peak magnetic gradient. The gain of the sensor is automatically adjusted, keeping the internal electrical signal amplitude constant over the air gap range, AG, of the device. This feature provides consistent operational char- acteristics independent of variances in the air gap. Switch Points. Switch points are the levels of magnetic fl ux density, B, which trigger switch turn-on and turn-off. When B exceeds a certain limit, referred to as the Operate point (B op), the trigger provides a clean transition from off to on. When the magnetic fi eld falls below B op by a certain limit, referred to as the Release point, Brp, the trigger provides a clean transition from on to off. In the ATS672, switch points are established dynamically as a percentage of the amplitude of the normalized magnetic signal. Two DACs track the peaks of the normalized magnetic signal, and the switching thresholds are established at fi xed percentages of the two DAC values. The values of the thresholds have been carefully selected to provide the most accurate and consistent switching where the signal is steepest and least affected by air gap variation. The fi gure below graphically demonstrates the establishment of the switching threshold levels. The low hysteresis of 10% provides high performance over the full AG, and immunity to false switching due to noise, vibration, backlash, or other transient events. Mechanical Profile Magnetic Gradient AGMin AGMax AGMin AGMax (No amplification) Electrical Signal Response, with AGC Ferrous Target 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. 100% Valley Signal Tooth Signal Bop Brp Bop% Brp% Bhys t V Switch Points. The ATS672 design minimizes hysteresis, Bhys.
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Target Sensor
Application Information
The Hall-effect sensor can detect variations in magnetic fl ux density generated by features of a target. To distinguish between two features of a target, such as between a tooth and a valley of a spur gear, there must be a minimum differential of 120 G in the magnetic fl ux densities corresponding to the features, as measured at the sensor. The target must be mounted with an air gap in the range AG, the distance between the target object and the plane of the Hall- effect sensor as installed. In general, the nearer a target feature is to the active area of the sensor, the greater the magnetic fl ux density at the sensor. The following fi gures and table specify a design that can be used to construct a reference target. The target represents a ferrous spur gear, with uniform tooth and valley widths. The target would be mounted so that its axis of rotation is parallel to the plane of the Hall-effect sensor element, and centered on the ele- ment. When the target is produced to the specifi cations listed in the Reference Target column of the table, the required differen- tial (tooth peak to valley) in magnetic fl ux densities is generated. Also in the table, the Minimum Required for TPOS column provides specifi cations for a similar application. These values are the minimum required for the TPOS function to operate accu- rately, as defi ned in the Operating Characteristics table. Reference Target Characteristics Characteristic Symbol Description Reference Target 8X Only Minimum Required for TPOS Units Material Target has uniform composition CRS1018 – – Diameter D O Diameter of target, to valley 120 – mm Tooth Thickness F Breadth of tooth, with respect to sensor 6 5 mm Tooth Height H t Height of tooth, measured from the valley (DO)5 5m m Tooth Width T Width of tooth 22.5* 5 deg. Valley Width P C – T Width of valley, with P C = pitch of teeth 22.5* 13 deg. *Resulting arc measures 23.6 mm in length at DO 8X Reference Target For additional general application information, visit the Allegro MicroSystems Web site at www. allegromicro.com.
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Typical Circuit Design The following circuit is the most basic confi guration required for proper device operation. A pull-up resistor is used.
2 ATS672
0.1 uF VOUT Sensor/Target Evaluation In order to establish the proper operating specifi cation for a particular sensor/target confi guration, a systematic evaluation of the magnetic circuit should be performed. The fi rst step is the generation of a magnetic map of the target. By using a cali- brated device, a magnetic signature of the system is made. A magnetic map of the 8X reference target, created using the LSB sensor package, is shown below. From this map data, a pair of curves can be derived that describe the tooth and valley magnetic fi elds versus air gap. Knowing the minimum amount of magnetic fl ux density that guarantees operation of the sensor, one can determine the maximum opera- tional air gap of the sensor/target system. Magnetic Map,8X Reference Target, Using LSB Package -200 -150 -100 -50 100 150 200 250 300 350 400 450 500 0 30 60 90 120 150 180 210 240 270 300 330 360 Position (°) Magnetic Flux Density, B (G) -200 -100 100 200 300 400 500 600 Air Gap (mm) Magnetic Flux Density, B (G) 8X Reference Target Using LSB Package Magnetic Flux Density, B, Versus Air Gap Tooth Valley
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB SENSOR EVALUATION: ACCURACY The self-calibration algorithm allows the sensor to adapt to system changes such as air gap increase. However, major changes in air gap can adversely affect switching performance. When characterizing sensor performance over a signifi cant air gap range, be sure to power-off and then power-on the device at each air gap. This ensures that self-calibration occurs for each installation condition. See the Operating Charactersitics table for information on timing accuracy performance. Edge Position vs. Air Gap Electrical Rising Edge (Mechanical Falling Edge) 103 103.2 103.4 103.6 103.8 104 104.2 104.4 104.6 104.8 105 Air Gap (mm) Edge Position (Degrees) ROOM 150ºC -40ºC Edge Position vs. Air Gap Electrical Falling Edge (Rising Mechanical Edge) ATS672LSB; 8X Reference Target 125 125.2 125.4 125.6 125.8 126 126.2 126.4 126.6 126.8 127 Air Gap (mm)) Edge Position (Degrees) ROOM 150ºC -40ºC ATS672LSB; 8X Reference Target Target Relative Timing Accuracy Device Output TAbsRise (Max - Min) TAbsFall (Max - Min) Tooth Operational Air Gap Valley Air Gap
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Temperature Compensation The device should be operated at or below the maximum junc- tion temperature of the device, TJ(max) (see the Absolute Maxi- mum Ratings section, on page 1). The actual operating TJ of the device is affected by several factors. Under certain combinations of peak conditions (corresponding to the gray area of the Power De-Rating Curve chart), operation may require power de-rating or heat sinking. The relevent factors are characteristic of the device and pack- age, as well as the application, including the effect of adjacent external sources of heat. The Package Thermal Resistance, R θJA, indicates the resitance to heat transfer from the heat-generating portions of the die (the “junction”) through all paths to the ambi- ent air. This includes heat sinking through the PCB, as well as direct radiation from the die through the package, R θCA. Thermal information on packages is available on the Allegro Web site. The Allowable Power Dissipation, PD, represents the amount of power that can be applied to the device at a given RθCA and ambient temperature, TA, without causing the temperature of the die to exceed , TJ(max). This section presents a procedure for cor- relating these factors with operating voltage, VCC, and operating current, ICC, to estimate their effect on TJ. If the estimated operating TJ exceeds TJ(max), then power levels can be reduced or external heat sinking can be applied. Typi- cally, V CC is the factor reduced, to accommodate the required TA. A power de-rating curve can be constructed, representing the maximum allowable VCC per TA. If the calculated VCC exceeds the power de-rating curve at the required TA, and heat sinking is not preferred, estimate the amount to reduce VCC. This can be estimated through calculat- ing PD(max), the maximum allowable PD for the given device and package. PD(max) is related to RθJA and TA. The following formu- las represent the fundamental relationships used to calculate the V CC adjustment, based on the temperature effect, ∆T. TJ = TA + ∆T (1) where ∆T denotes the increase in TJ due to power dissipation within the device. ∆T = PD × RθJA (2) PD = VCC × ICC (3) Examples for estimating VCC are provided on the next page. These formulas and results can also be used to estimate T J. For example, given common conditions such as: T A= 25°C, VCC = 5 V, ICC(on) = 6.5 mA, and RθJA = 150 °C/W then: P D = VCC × ICC(on) = 5 V × 6.5 mA = 32.5 mW ∆ T = PD × RθJA = 32.5 mW × 150 °C/W = 4.9°C 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 20 40 60 80 100 120 140 160 180 Maximum Allowable VCC (V) TA (ºC) Allowable operating range without additional heat sinking Some combinations of peak ratings may require heat sinking when operating in shaded area VCC(max) = 26.5 V; TJ(max) = 170ºC Power De-Rating Curve
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Example: VCC Adjustment, Package SE Observe the absolute maximum ratings for the package, specifi cally: R θJA = 150 °C/W T J(max) = 170°C Also observe the characteristic operating maximums: V CC(max) = 26.5 V I CC(max) = 11 mA For a given TA (e.g., 150°C), fi rst calculate the Maximum Allow- able Power Dissipation, PD(max). Invert equation 1: ∆Tmax = TJ(max) – TA = 170°C – 150°C = 20°C This provides the allowable increase to TJ resulting from internal power dissipation. Then, invert equation 2: PD(max) = ∆Tmax ÷ RθJA = 20°C ÷ 150 °C/W = 133 mW This provides the corresponding allowable increase in power level. Finally, invert equation 3 to determine the corresponding supply voltage V CC: VCC = PD(max) ÷ ICC(max) = 133 mW ÷ 11 mA = 12 V The result indicates that the device and package can dissipate adequate amounts of heat at voltages up to 12 V , at TA = 150ºC. Because VCC(max) is more than the calculated VCC, however, the device requires additional heat sinking for operation between the calculated V CC and VCC(max), under these conditions. If the cal- culated VCC were greater than or equal to VCC(max), then opera- tion up to VCC(max) would not require additional heat sinking. vs. Ambient Temperature Maximum Power D issipation Package SB: RθJA = 150ºC/W, TJ(max) = 170ºC 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 20 40 60 80 100 120 140 160 180 PD(max) (mW) TA (ºC)
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB Package SB, 4-pin SIP AAD 0.42
30Dec03, Rev. 1.42 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Allegro MicroSystems, Inc. Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture ATS672LSB The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 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 de par tures from the detail spec i fi ca tions as may be required to permit improvements in the per for mance, 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 compo- nents in life-support devices or sys tems without express written approval. The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon - si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. Copyright © 2004 Allegro MicroSystems, Inc.