ATS665LSG

ATS665LSG True Zero Speed, High Accuracy, Gear Tooth Sensor The ATS665 true zero-speed gear tooth sensor is an optimized Hall IC/magnet configuration packaged in a molded module that provides a user-friendly solution for digital gear tooth sensing applications. The sensor module consists of an over-molded package, which holds together a samarium cobalt magnet, a pole piece and a true zero-speed Hall IC that has been optimized to the magnetic circuit. This small package can be easily assembled and used in conjunction with gears of various shapes and sizes. The sensor incorporates a dual element Hall IC that switches in response to differential magnetic signals created by a ferrous target. The IC contains a sophisticated compensating circuit designed to reduce the detrimental effects of magnet and system offsets. Digital processing of the analog signal provides zero speed performance independent of air gap and also dynamic adaptation of device performance to the typical operating conditions found in automotive applications (reduced vibration sensitivity). Highresolution 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 associated with the targets used in many automotive applications. This sensor’s ability to provide tight duty cycle at high speeds and over a wide temperature range makes it ideal for transmission and industrial speed applications. The ATS665 is available in the SG package in the automotive temperature range, -40° to 150° (L). FEATURES & BENEFITS True zero-speed operation Switchpoints independent of air gap High vibration immunity Precise duty cycle signal over operating temperature range Large operating air gaps Defined power-on state Wide operating voltage range Digital output representing target profile Single-chip sensing IC for high reliability Small mechanical size Optimized Hall IC magnetic system 200 µs power-on time at gear speed < 100 rpm AGC and reference adjust circuit Under-voltage lockout Pin 1: VCC Pin 2: VOUT Pin 3: Tie to Gnd or Float Pin 4: Gnd Supply Voltage 1 , VCC . . . . . . . . . . . . . . . . . . . . . . . . . . 26.5 V Reverse Supply Voltage, VRCC . . . . . . . . . . . . . . . . . . . . . . . . . . –18 V Reverse Output Current 2 , IRCC. . . . . . . . . . . . . . . . . . . . . . . . . . . 50 mA Continuous Output Current, IOUT . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA Ambient Operating Temperature Range, TA . . . . . . . . . . . . . . . . . . -40° C to 150°C Storage Temperature, TS . . . . . . . . . . . . . . . . . . . . -65° C to 170°C Maximum Junction Temperature, TJmax . . . . . . . . . . . . . . . . . . . . . . . . . 165° C ABSOLUTE MAXIMUM RATINGS Order by: ATS665LSGTN-T (Pb-free, 800 pieces/reel). 1 2 Refer to power de-rating curve VOUT ≥ -0.5V (Pb-based variants are being phased out of the product line. ATS665LSGTN is 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.) Rev.1 ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR OPERATING CHARACTERISTICS Valid at TA = -40oC to 150oC over air gap, unless otherwise noted Typical operating parameters: Vcc = 12 V and TA = 25°C Limits Min. ELECTRICAL CHARACTERISTICS Supply Voltage Under Voltage Lockout Reverse Supply Current Supply Zener Clamp Voltage Supply Zener Current Supply Current VCC VCC(UV) IRCC VZ IZ ICC VCC = –18 V Icc = IcconMAX + 3mA,TA = 25°C Test only; VCC = 28V, Tj < Tj(max) Output OFF Output ON Operating; Tj < Tjmax 3.3 – – 26.5 – – – – Gear Speed < 100 RPM; VCC > VCC min Output = ON, ISINK = 20 mA VOUT = 12 V, Tj < Tj(max) Output = OFF, VOUT = 24 V RLOAD = 500 Ω, CLOAD = 10 pF RLOAD = 500 Ω, CLOAD = 10 pF Reference target % of peak-to-peak signal, AG < AG (max) % of peak-to-peak signal, AG < AG (max) – – 25 – – – 0 – – – – – – – – 8 8 High – 225 45 – 1.0 0.6 – 20 70 30 24 < Vcc min –10 – Icconmax +3 14 14 – 200 400 70 10 2 2 12000 – – – μs mV mA μA μs μs rpm kHz % % V V mA V mA mA mA Typ. Max. Units Characteristics Symbol Test Conditions POWER-ON STATE CHARACTERISTICS Power-On State Power-On Time OUTPUT STAGE Low Output Voltage Output Current Limit Output Leakage Current Output Rise Time Output Fall Time Target Speed Bandwidth Operate Point Release Point VSat Ilim IOFF tr tf S f-3dB BOP B SPO tPO SWITCH POINT CHARACTERISTICS BRP Final Version, Rev 2.0; MN; 19Dec05 Page 2 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR CALIBRATION Initial Calibration Calibration Update Start-up 3 Running mode operation – 2 Continuous 6 Edges OPERATING CHARACTERISTICS (with 60-0 reference target) Measured from sensor face to top of Operational Air Gap AG target tooth Duty Cycle AG < AG (max), reference target Operating Signal Duty cycle spec compliance 0.5 42 60 – 47 – 2.5 52 – mm % G REFERENCE TARGET/GEAR INFORMATION 3 Power-on speed ≤ 200 rpm Diameter Thickness Tooth Width Valley Width Valley Depth Material 120 6 3 3 3 mm mm mm mm mm Low carbon steel Final Version, Rev 2.0; MN; 19Dec05 Page 3 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR SENSOR DESCRIPTION Assembly Description: The ATS665 true zero speed gear tooth sensor is 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. Sensing Technology: The gear tooth sensor sub-assembly contains a single-chip differential Hall effect sensor IC, a Samarium Cobalt magnet, and a flat ferrous pole piece. The Hall IC consists of two Hall elements spaced 2.2 mm apart which measure the magnetic gradient created by the passing of a ferrous object. The gradient is converted to an analog voltage that is then processed to provide a digital output signal. Final Version, Rev 2.0; MN; 19Dec05 Page 4 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR Operation: After proper power is applied to the component the sensor is then capable of providing digital information that is representative of the profile 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. The following output diagram is indicative of the sensor performance for the polarity indicated in the figure at the bottom of the page. MECHANICAL PROFILE MAGNETIC PROFILE SENSOR ELECTRICAL OUTPUT PROFILE Output Polarity: The output of the sensor will switch from LOW to HIGH as the leading edge of the tooth passes the sensor face in the direction indicated in the figure below. In this system configuration, the output voltage will be high when the sensor is facing a tooth. If rotation occurs in the opposite direction, the output polarity will invert. High over Tooth Power-On State Operation: The device is guaranteed to power up in the OFF state (logic high output). Final Version, Rev 2.0; MN; 19Dec05 Page 5 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR Start-up Detection: Since the sensor powers up in the OFF state (logic high output), the first edge seen by the sensor can be missed if the switching induced by that edge reinforces the OFF state. Therefore, the first edge that can be guaranteed to induce an output transition is the second detected edge. This device has accurate first electrical falling edge detection. The tables below show various start-up schemes. MECHANICAL TARGET PROFILE MAGNETIC PROFILE (High over Tooth) High over Tooth SENSOR OUTPUT (Start-up over Valley) SENSOR OUTPUT (Start-up over Rising Edge) SENSOR OUTPUT (Start-up over Tooth) SENSOR OUTPUT (Start-up over Falling Edge) Sensor start-up location MECHANICAL TARGET PROFILE MAGNETIC PROFILE (Low over Tooth) SENSOR OUTPUT (Start-up over Valley) Low over Tooth SENSOR OUTPUT (Start-up over Rising Edge) SENSOR OUTPUT (Start-up over Tooth) SENSOR OUTPUT (Start-up over Falling Edge) Sensor start-up location Final Version, Rev 2.0; MN; 19Dec05 Page 6 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR Under-Voltage Lockout: When the supply voltage falls below the minimum operating voltage (VccUV), the device turns OFF and stays OFF irrespective of the state of the magnetic field. This prevents false signals caused by under-voltage 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 supply voltage 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. The following circuit is the most basic configuration required for proper device operation. For EMC information, contact your Allegro representative. Internal Electronics: The ATS665 contains a self-calibrating Hall effect IC that possesses two Hall elements, 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 using a proprietary BiCMOS process. Changes in temperature do not greatly affect this device due to the stable amplifier design and the offset rejection circuitry. Vcc Vsig INTERNAL HALL AMP AUTOMATIC GAIN CONTROL REGULATOR THRESHP THRESHOLD COMPARATOR OUTPUT REFERENCE GENERATOR THRESH LOGIC Output Transisto r PDAC PPEAK THRESHN Current Limit NDAC NPEAK GND Final Version, Rev 2.0; MN; 19Dec05 Page 7 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR SENSOR OPERATION: AUTOMATIC GAIN CONTROL (AGC) The patented self-calibrating circuitry is unique. After each power up, the device measures the peak-to-peak magnetic signal. The gain of the sensor is then adjusted which keeps the internal signal amplitude constant over the air gap range of the device. This feature provides operational characteristics independent of air gap. DIFFERENTIAL MAGNETIC SIGNAL WITH INCREASING AIR GAP 1000 DIFFERENTIAL ELECTRICAL SIGNAL WITH INCREASING AIR GAP 1000 DIFFERENTIAL SIGNAL [mV] 800 600 400 200 0 -200 -400 -600 -800 -1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 TARGET POSITION [DEGREES] 0.25 mm 0.50 mm 1.00 mm 1.50 mm 2.00 mm MAGNETIC FLUX DENSITY [GAUSS] 800 600 400 200 0 -200 -400 -600 -800 0.25 mm 0.50 mm 1.00 mm 1.50 mm 2.00 mm -1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 TARGET POSITION [DEGREES] Magnetic Signal with no Amplification Electrical Signal after AGC SENSOR OPERATION: OFFSET ADJUST In addition to normalizing performance over air gap, the gain control circuitry also reduces the effect of chip, magnet, and installation offsets. This is accomplished using two D/A converters that capture the peak and valley of the signal and use it as a reference for the switching comparator. If induced offsets bias the absolute signal up or down, AGC and the dynamic DAC behavior work to normalize and reduce the impact of the offset on sensor performance. Final Version, Rev 2.0; MN; 19Dec05 Page 8 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR SENSOR OPERATION: SWITCHPOINTS Switchpoints in the ATS665 are established dynamically as a percentage of the amplitude of the normalized magnetic signal. Two DACs track the peaks of the normalized magnetic signal (see the section on Update); the switching thresholds are established at 30% and 70% of the two DAC’s values. The proximity of the thresholds near 50% ensures the most accurate and consistent switching where the signal is steepest and least affected by air gap variation. The hysteresis of 40% provides high air gap performance and immunity to false switching on noise, vibration, backlash and other transient events. Since the hysteresis value is independent of air gap, it provides protection against false switching in the presence of overshoot that can be induced on the edges of large teeth. The figure below graphically demonstrates the establishment of the switching threshold levels. Switching Threshold Levels Bop 100 % 70 % 30 % 0% Brp Because the threshold are established dynamically as a percentage of the peak-peak signal, the effect of a baseline shift is minimized. As a result, the effects of offsets induced by tilted or off-center installation are minimized. Final Version, Rev 2.0; MN; 19Dec05 Page 9 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR SENSOR OPERATION: UPDATE The ATS665 incorporates an algorithm that continuously monitors the system and updates the switching thresholds accordingly. The switch point for each edge is determined by the previous two edges. Since variations are tracked 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. The figures below show how the sensor uses historical data to provide the switching threshold for a given edge. Switching Level - Operate Operate point based on previous two peaks Switching Level - Release Release point based on previous two peaks Final Version, Rev 2.0; MN; 19Dec05 Page 10 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR SENSOR/TARGET EVALUATION In order to establish the proper operating specification for a particular sensor/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 signature of the system is made. The following is a map of the 60-0 reference target. Flux density shown is the differential of the magnetic fields sensed at the two Hall elements. 300 250 200 150 Flux Density [Gauss] 100 50 0 -50 -100 -150 -200 -250 -300 0 5 10 15 20 25 30 35 0.94mm 1.19mm 1.44mm 1.69mm 1.94mm 2.19mm 2.44mm 2.69mm 2.94mm 3.19mm Position [º] A single curve is distilled from this map data that describes the peak-peak magnetic field versus air gap. Knowing the minimum amount of magnetic flux density that guarantees operation of the sensor, one can determine the maximum operational air gap of the sensor/target system. Referring to the chart below, a minimum required peak-peak signal of 60G corresponds to a maximum air gap of approximately 2.5 mm. ATS665LSG 60-0 TARGET MAP 700 600 Peak-Peak Flux Density [Gauss] 500 400 300 200 100 0 0.5 1 1.5 2 Air Gap [mm] 2.5 3 3.5 Final Version, Rev 2.0; MN; 19Dec05 Page 11 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR TARGET DESIGN For the generation of adequate magnetic field levels to maximize air gap performance, the following recommendations should be followed in the design and specification of targets. • • • • • Tooth width > 2 mm Valley width > 2 mm Valley depth > 2 mm Gear thickness > 3 mm Target material must be low carbon steel Though these parameters apply to targets of traditional geometry (radially oriented teeth with radial sensing), they can be applied to stamped targets as well. For stamped geometries with axial sensing, the valley depth is intrinsically infinite so the criteria for tooth width, valley width, material thickness (can be < 3 mm) and material specification need only be considered. SENSOR EVALUATION: ACCURACY While the update algorithm will allow the sensor the adapt to system changes (i.e. air gap increase), major changes in air gap can adversely affect switching performance. When characterizing sensor performance over a significant air gap range, be sure to re-power the device at each air gap. This ensures that self-calibration occurs for each installation condition. See the section entitled Characteristic Data for typical duty cycle performance. Final Version, Rev 2.0; MN; 19Dec05 Page 12 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR POWER DE-RATING Due to internal power consumption, the junction temperature of the IC, Tj, is higher than the ambient environment temperature, Ta. To ensure that the device does not operate above the maximum rated junction temperature use the following calculations: ΔT = PD * Rθja Where: PD = Vcc * Icc ∴ ΔT=Vcc * Icc * Rθja Where ΔT denotes the temperature rise resulting from the IC’s power dissipation. Tj = Ta + ΔT For the sensor : Tj(max) = 165°C Rθja = 126°C/W Typical Tj calculation: Ta = 25 °C Vcc = 5 V Icc = 7.0 mA PD = Vcc * Icc = 5 V * 8.0 mA = 40.0 mW Maximum Supply Voltage [Volts] 30.0 28.0 26.0 24.0 22.0 20.0 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 20 40 60 80 Tj = Ta + ΔT Then, at Ta = 150 °C: ΔTmax = Tjmax – Tamax = 165°C - 150°C = 15°C If: ΔT = PD * Rθja Then, at Ta = 150°C: PDmax = ΔTmax / Rθja = 15°C / 126°C/W = 119 mW If: PD = Vcc * Icc Then the maximum Vcc at 150°C is therefore: Vccmax = PDmax / Icc = 119 mW / 12.0 mA = 9.9 V This value applies only to the voltage drop across the 665 chip. If a protective series diode or resistor is used, the effective maximum supply voltage is increased. For example, when a standard diode with a 0.7 V drop is used: Vsmax = 9.9 V + 0.7 V = 10.6 V ATS665LSG Package Power De-Rating Curve Thermal Resistance = 126°C/Watt, Tjmax = 165°C ΔT = PD * Rθja = 40.0 mW * 126°C/W = 5.0°C Tj = Ta + ΔT = 25 °C + 5.0°C = 30.0°C Maximum Allowable Power Dissipation Calculation for ATS665: Assume: Ta = Tamax = 165 °C Tj(max) = 165°C Icc = 12.0 mA 4 If: 4 c 100 120 140 160 180 Ambient Temperature [°C] max Icc @ 150C < max Icc @ 25C, see characteristic data Final Version, Rev 2.0; MN; 19Dec05 Page 13 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR CHARACTERISTIC DATA IccOn 14 12 10 Icc [mA] 8 6 4 2 0 0 10 Vcc [V] 20 30 -40 0 25 85 150 IccOn 14 12 10 Icc [mA] 4.3 8 6 4 2 0 -50 0 50 100 150 Temperature [°C] 12 20 26.5 Vcc °C IccOff IccOff 14 12 10 Icc [mA] 8 6 4 2 0 0 10 Vcc [V] 20 30 Icc [mA] -40 0 25 85 150 14 12 10 4.3 8 6 4 2 0 -50 0 50 100 150 Temperature [°C] 12 20 26.5 Vcc °C Vsat 400 Output Voltage [mV] 350 300 250 200 150 100 50 -50 0 50 100 150 200 Temperature [°C] Final Version, Rev 2.0; MN; 19Dec05 Page 14 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR CHARACTERISTIC DATA (Continued) Duty Cycle 100 RPM 53 52 51 50 49 48 47 46 45 44 43 -50 0 50 100 150 Temperature [°C] 53 52 51 Duty Cycle [% ] 50 49 48 47 46 45 44 43 0 1 Air Gap [mm] 2 3 -40 0 25 85 150 °C Duty Cycle 100 RPM Duty Cycle [% ] 0.4 0.5 0.8 1.5 2.35 2.5 Air gap Duty Cycle 1000 RPM 53 52 51 50 49 48 47 46 45 44 43 -50 0 50 100 150 Temperature [°C] 53 52 Duty Cycle [% ] Duty Cycle @ 1000 RPM Duty Cycle [% ] 0.4 0.5 0.8 1.5 2.35 2.5 Air gap 51 50 49 48 47 46 45 44 43 0 1 Air Gap [mm] 2 3 -40 0 25 85 150 °C Final Version, Rev 2.0; MN; 19Dec05 Page 15 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR PACKAGE DRAWING Final Version, Rev 2.0; MN; 19Dec05 Page 16 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc. ATS665LSG TRUE ZERO-SPEED GEAR TOOTH SENSOR RELATED DOCUMENTS Documents that can be found on the Allegro Microsystems 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) • • • • Additional Applications Information on gear tooth and other Allegro sensors can be obtained at Allegro’s web site, www.allegromicro.com Final Version, Rev 2.0; MN; 19Dec05 Page 17 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995, 2005 Allegro MicroSystems, Inc.