ATS643LSH-I1TN

ATS643LSH Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update Last Time Buy This part is in production but has been determined to be LAST TIME BUY. This classification indicates that the product is obsolete and notice has been given. Sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because of obsolescence in the near future. Samples are no longer available. Date of status change: May 2, 2011 Deadline for receipt of LAST TIME BUY orders: October 31, 2011 Recommended Substitutions: For existing customer transition, and for new customers or new applications, refer to the ATS685. 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. ATS643LSH Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update Features and Benefits Description ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ The ATS643 is an optimized combination of integrated circuit and rare-earth pellet that provides a manufacturer-friendly solution for true zero-speed digital gear-tooth sensing in twowire applications. The device consists of a single-shot molded plastic package that includes a samarium cobalt pellet, a pole piece, and a Hall-effect IC that has been optimized to the magnetic circuit and the automotive environment. This small package can be easily assembled and used in conjunction with a wide variety of gear shapes and sizes. Fully-optimized differential digital gear tooth sensor IC Single chip-IC for high reliability Internal current regulator for 2-wire operation Small mechanical size (8 mm diameter x 5.5 mm depth) Switchpoints air gap independent Digital output representing gear profile Precise duty cycle accuracy throughout temperature range Large operating air gaps 1 Side) (Pin 1 Side) Figure 1. Relative motion of the target is detected by the dual Hall elements mounted on the Hall IC. This tooth sensed earlier This tooth sensed later Target (Gear) Target Magnetic Profile +B Package Orientation to Target Package Branded Face Pin 4 Side Pin 1 Side Package IC Internal Differential Analog Signal, VPROC BOP(#1) BOP(#2) +t BRP(#1) Branded Face of Package Rotating Target IC Internal Switch State Off On Off On +t 1 4 IC Output Signal, IOUT +t Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation results in a high output signal when a tooth of the target gear is nearest the face of the package (see figure 3). A right-to-left (pin 4 to pin 1) rotation inverts the output signal polarity. Figure 3. The magnetic profile reflects the geometry of the target, allowing the ATS643 to present an accurate digital output response. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update ATS643LSH induced by the target and sensed by the Hall elements. When VPROC transitions through a switchpoint from the appropriate higher or lower level, it triggers IC switch turn-on and turn-off. As shown in figure 3, when the switch is in the off state, as VPROC rises through a certain limit, referred to as the operate point, BOP , the switch toggles from off to on. When the switch is in the on state, as VPROC falls below BOP to a certain limit, the release point, BRP , the switch toggles from on to off. (A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift As shown in panel C of figure 4, threshold levels for the ATS643 switchpoints are established dynamically as function of the peak input signal levels. The ATS643 incorporates an algorithm that continuously monitors the system and updates the switching thresholds accordingly. The switchpoint for each edge is determined by the detection of the previous two edges. In this manner, variations are tracked in real time. (B) Internal analog signal, VPROC, typically resulting in the IC V+ Smaller TEAG IC Target Smaller TEAG Larger TEAG VPROC (V) Target Hysteresis Band (Delimited by switchpoints) Larger TEAG IC Smaller TEAG 0 360 Target Rotation (°) (C) Referencing the internal analog signal, VPROC, to continuously update device response 1 2 3 4 Determinant Peak Values BOP(#1) BRP(#1) Pk(#1), Pk(#2) Pk(#2), Pk(#3) BOP(#2) BRP(#2) Pk(#3), Pk(#4) Pk(#4), Pk(#5) BOP(#3) BRP(#3) Pk(#5), Pk(#6) Pk(#6), Pk(#7) BOP(#4) Pk(#7), Pk(#8) BRP(#4) Pk(#8), Pk(#9) V+ Pk(#9) Pk(#1) Pk(#3) Pk(#7) Pk(#5) VPROC (V) BHYS Switchpoint BOP(#1) BOP(#2) BOP(#4) BOP(#3) BRP(#1) BRP(#3) BRP(#2) Pk(#4) BRP(#4) Pk(#6) Pk(#8) Pk(#2) BHYS(#1) BHYS(#2) BHYS(#3) BHYS(#4) t+ Figure 4. The Continuous Update algorithm allows the Allegro IC 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 IC 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update ATS643LSH Power-On State Operation. The ATS643 is guaranteed to power-on in the high current state, ICC(High). Initial Edge Detection. The device self-calibrates using the initial teeth sensed, and then enters Running mode. This results in reduced accuracy for a brief period (less than four teeth), however, it allows the device to optimize for continuous update yielding adaptive sensing during Running mode. As shown in figure 5, the first three high peak signals are used to calibrate AGC. However, there is a slight variance in the duration of initialization, depending on what target feature is nearest the package when power-on occurs. Target (Gear) 1 Package Position 2 3 4 VPROC Power-on over valley 1 Output Start Mode Hysteresis Overcome AGC Calibration Running Mode VPROC Power-on at rising edge 2 Output Start Mode Hysteresis Overcome AGC Calibration Running Mode AGC Calibration Running Mode VPROC Power-on over tooth 3 Output Start Mode Hysteresis Overcome VPROC Power-on at falling edge 4 Output Start Mode Hysteresis Overcome AGC Calibration Running Mode Figure 5. Power-on initial edge detection. This figure demonstrates four typical power-on scenarios. All of these examples assume that the target is moving relative to the package in the direction indicated. The length of time required to overcome Start Mode Hysteresis, as well as the combined effect of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when AGC calibration begins. Three high peaks are always required for AGC calibration. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update ATS643LSH Start Mode Hysteresis. This feature helps to ensure optimal self-calibration by rejecting electrical noise and low-amplitude target vibration during initialization. This prevents AGC from calibrating the IC on such spurious signals. Calibration can be performed using the actual target features. A typical scenario is shown in figure 6. The hysteresis, POHYS, is a minimum level of the peak-to-peak amplitude of the internal analog electrical signal, VPROC, that must be exceeded before the ATS643 starts to compute switchpoints. Target, Gear Package Position Relative to Target 1 5 2 Target Magnetic Profile Differential Signal, VPROC BRP(#1) Start Mode Hysteresis, POHYS BOP(#1) 1 BOP(#2) 2 3 4 5 Output Signal, IOUT Figure 6. Operation of Start Mode Hysteresis Position 1. At power-on, the ATS643 begins sampling VPROC. Position 2. At the point where the Start Mode Hysteresis is exceeded, the device begins to establish switching thresholds (BOP and BRP) using the Continuous Update algorithm. After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid VPROC value exceeding the Start Mode Hysteresis can be generated either by a legitimate target feature or by excessive vibration. Position 3. In this example, the first switchpoint transition is through BOP . and the output transitions from high to low. If the first switchpoint transition had been through BRP (such as position 4), no output transition would occur because IOUT already would be in the high polarity. The first transition would occur at position 5 (BOP). Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update ATS643LSH Undervoltage Lockout. When the supply voltage falls below the minimum operating voltage, VCC(UV), ICC goes high and remains high regardless of the state of the magnetic gradient from the target. This lockout feature prevents false signals, caused by undervoltage conditions, from propagating to the output of the IC. Power Supply Protection. 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 application circuit. 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). At power- on, the device determines the peak-to-peak amplitude of the signal generated by the target. The gain of the IC is then automatically adjusted. Figure 8 illustrates the effect of this feature. Automatic Offset Adjust (AOA). The AOA is patented circuitry that automatically cancels 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 power-on mode and running mode, compensating for any offset drift. Continuous operation also allows it to compensate for offsets induced by temperature variations over time. Assembly Description. The ATS643 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. Ferrous Target Mechanical Profile V+ VCC (Optional) 1 2 ATS643 3 Internal Differential Analog Signal Response, without AGC AGSmall 0.01 μF (Optional) AGLarge V+ 4 100 Ω Figure 7. Typical basic circuit for proper device operation. Internal Differential Analog Signal Response, with AGC AGSmall AGLarge Figure 8. Automatic Gain Control (AGC). The AGC function corrects for variances in the air gap. Differences in the air gap cause differences in the magnetic field at the device, but AGC prevents that from affecting device performance, a shown in the lowest panel. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 ATS643LSH Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update 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, RJA, 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, RJC, is relatively small component of RJA. 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) T = PD × RJA (2) TJ = TA + ΔT Example: Reliability for VCC at TA = 150°C, package L-I1, using minimum-K PCB Observe the worst-case ratings for the device, specifically: RJA = 126°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and ICC(max) = 16 mA. Calculate the maximum allowable power level, PD(max). First, invert equation 3: 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 ÷ RJA = 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 RJA. 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 RJA = 140 °C/W, then: PD = VCC × ICC = 12 V × 4 mA = 48 mW  T = PD × RJA = 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 RJA and TA. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 Self-Calibrating, Zero-Speed Differential Gear Tooth Sensor IC with Continuous Update ATS643LSH Package SH, 4-pin SIP F 5.50±0.05 1.10 E 1.10 F 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 Copyright ©2004-2009, Allegro MicroSystems, Inc. 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 15