Data Sheet 27612A† 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED The A3046EU/LU, A3056EU/LU, and A3058EU/LU Hall effect gear-tooth sensors are monolithic integrated circuits that switch in response to differential magnetic fields created by ferrous targets. These devices are ideal for use in gear-tooth-based speed, position, X X and timing applications and operate down to zero rpm over a wide range of air gaps and temperatures. When combined with a back- biasing magnet and proper assembly techniques, devices can be configured to give 50% duty cycle or to switch on either leading, trailing, or both edges of a passing gear tooth or slot. V The six devices differ only in their magnetic switching values and CC operating temperature ranges. The low hysteresis of the A3046/56EU and A3046/56LU makes them perfectly suited for ABS (anti-lock brake system) or speed sensing applications where maintaining large air 1 2 3 gaps is important. The A3046EU/LU features improved switch point stability with temperature over the A3056EU/LU. The high hysteresis of the A3058EU and A3058LU, with their excellent temperature stability, makes them especially suited to ignition timing applications where switch-point accuracy (and latching requirements) is extremely important. Continued next page... BENEFITS Dwg. PH-012 � Senses Ferrous Targets Down to Zero RPM Pinning is shown viewed from branded side. � Large Effective Air Gap � Wide Operating Temperature Range � Operation from Unregulated Supply ABSOLUTE MAXIMUM RATINGS � High-Speed Operation � Output Compatible With All Logic Families Supply Voltage, V . . . . . . . . . . . . . . 28 V CC � Reverse Battery Protection Reverse Battery Voltage, � Solid-State Reliability V . . . . . . . . . . . . . . . . . . . . . . -30 V RCC Magnetic Flux Density, B . . . . . Unlimited � Resistant to Physical Stress Output OFF Voltage, V . . . . . . . . . 28 V OUT SELECTION GUIDE . . . . . -0.5 V Reverse Output Voltage, V OUT Output Current, I . . . . . . . . . . . . 25 mA OUT Switching Hysteresis . . 500 mW Package Power Dissipation, P D 15-90 G 150-250 G Operating Temperature Range, T A Operating Temp. Range Device Type Number Suffix “EU” . . . . . . . . . -40°C to +85°C -40°C to +85°C A3046EU A3058EU Suffix “LU” . . . . . . . . -40°C to +150°C A3056EU Storage Temperature Range, T . . . . . . . . . . . . . . . -65°C to +170°C -40°C to +150°C A3046LU A3058LU S A3056LU SUPPLY GROUND OUTPUT 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED All devices, when used with a back- biasing magnet, can be configured to turn ON FUNCTIONAL BLOCK DIAGRAM or OFF with the leading or trailing edge of a gear tooth or slot. Changes in fields on the 1 SUPPLY magnet face caused by a moving ferrous mass are sensed by two integrated Hall transducers and are differentially amplified by on-chip electronics. The on-chip temperature compensation and Schmitt trigger circuitry REG minimizes shifts in effective working air gaps OUTPUT and switch points over temperature making 3 these devices ideal for use in ignition timing, + anti-lock braking systems, and speed mea- – surement systems in hostile automotive and 2 industrial environments. X X GROUND Each Hall effect digital Integrated circuit includes two quadratic Hall effect sensing elements, a voltage regulator, temperature Dwg. FH-010 compensating circuitry, low-level amplifier, Schmitt trigger, and an open-collector output driver. The on-board regulator permits operation with supply voltages of 4.5 to 24 volts. The output stage can switch up to 20 Both magnetic characteristics are available in a choice of two operat- mA at conservatively specified repetition ing temperature ranges. Suffix EU devices have an operating range of rates to 20 kHz and is compatible with bipolar -40°C to +85°C while suffix LU devices feature an operating range of and MOS logic circuits. -40°C to +150°C. All devices are packaged in a 3-pin plastic SIP. ELECTRICAL CHARACTERISTICS at V = 8 V, over operating temperature range. CC Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Supply Voltage V Operating 4.5 — 24 V CC Power-Up State — 3058* only, Output is OFF — V = 0 4.5 V, B < B CC OP Output Saturation Voltage V I = 20 mA, B > B — 135 400 mV OUT(SAT) OUT OP Output Leakage Current I V = V = 24 V, B < B — — 5.0 µA OFF CC OUT RP Supply Current I V = 24 V, B < B — 7.2 14 mA CC CC RP Output Rise time t R = 820 Ω, C = 20 pF — 100 — ns r L L Output Fall time t R = 820 Ω, C = 20 pF — 100 — ns f L L 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1989, 1995 Allegro MicroSystems, Inc. 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED MAGNETIC CHARACTERISTICS in gauss at V = 8 V. CC Part Numbers* 3046 3056 3058 Characteristic Test Conditions Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. Operate Point, B Output Switches OFF to ON, — — 150 — — 150 — — 250 OP T = +25°C A Release Point, B Output Switches ON to OFF, -150 — — -150 — — -250 — — RP T = +25°C A Hysteresis, B B -B , T = +25°C 15 50 90 15 50 90 150 200 250 hys OP RP A Over operating temperature range, Change in Trip Point, — — ±50 — — ±75 — — ±50 Ref. B or B at T = +25°C ∆B or ∆B OP RP A OP RP NOTES: 1. Magnetic switch points are specified as the TYPICAL OPERATING CHARACTERISTICS difference in magnetic fields at the two Hall 200 elements. V = 8 V 2. As used here, negative flux densities are CC I = 20 mA OUT defined as less than zero (algebraic conven- 180 tion). 3. Typical values are at T = +25°C. A * Complete part number includes the prefix 160 ‘A’ and a suffix to identify operating tempera- ture range and package style. See selection 140 guide. 120 100 0 -50 50 100 150 AMBIENT TEMPERATURE IN °C Dwg. GH-033 10 11 V = 24 V T = +25°C CC A 10 9 B > B OP 9 8 B > B OP 8 B < B RP 7 7 B < B RP 6 6 5 5 0 510 15 20 25 -50 0 50 100 150 SUPPLY VOLTAGE IN VOLTS AMBIENT TEMPERATURE IN °C Dwg. GH-031 Dwg. GH-032 www.allegromicro.com SUPPLY CURRENT IN mA SATURATION VOLTAGE IN mV SUPPLY CURRENT IN mA 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED APPLICATIONS INFORMATION Figure 1 TYPICAL GEAR-TOOTH SENSING A gear-tooth sensing system consists of the sensor IC, a back- APPLICATION biasing magnet, an optional pole piece, and a target (Figure 1). The system requirements are usually specified in terms of the effective working air gap between the package and the target (gear teeth), the number of switching events per rotation of the target, temperature and BACK-BIASING speed ranges, minimum pulse duration or duty cycle, and switch point MAGNET accuracy. Careful choice of the sensor IC, magnet material and S shape, target material and shape, and assembly techniques enables large working air gaps and high switch-point accuracy over the system OPTIONAL POLE PIECE operating temperature range. Naming Conventions. With a south pole in front of the branded SENSOR IC surface of the sensor, a north pole behind the sensor, the field at the sensor is defined as positive. As used here, negative flux densities are A defined as less than zero (algebraic convention), e.g., -100 G is less than -50 G. Magnet Biasing. In order to sense moving non-magnetized ferrous targets, these devices must be back-biased by mounting the NS unbranded side on a small permanent magnet. Either magnetic pole (north or south) can be used. The devices can also be used without a back-biasing magnet. In this configuration, the sensor can be used to detect a rotating ring TARGET magnet such as those found in brushless dc motors or in speed GEAR sensing applications. Here, the sensor detects the magnetic field gradient created by the magnetic poles. Figure 2 TYPICAL TRANSFER CHARACTERISTIC Dwg. AH-003 24 V MAX B OP B RP V OUT(SAT) 0 -B 0+B DIFFERENTIAL FLUX DENSITY, BE1 – BE2 Dwg. GH-034 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 OUTPUT VOLTAGE IN VOLTS 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED Sensor Operation. The A3046EU/LU, A3056EU/LU, and A3058EU/LU sensor ICs Figure 3 each contain two integrated Hall transducers GEAR-TOOTH SENSOR OPERATION (E1 and E2) that are used to sense a mag- LEADING TRAILING netic field differential across the face of the EDGE EDGE IC (see SENSOR LOCATION drawing). Referring GEAR to Figure 2, the trigger switches the output ON (output LOW) when B – B > B and E1 E2 OP DIRECTION OF ROTATION switches the output OFF (output HIGH) when B – B < B . The difference between B E1 E2 RP OP E2 E1 and B is the hysteresis of the device. RP NORTH SOUTH Figure 3 relates the output state of a back-biased sensor IC, with switching 4300 G characteristics shown in Figure 2, to the target gear profile and position. Assume a B & B (a) E1 E2 north pole back-bias configuration (equivalent to south pole at the face of the device). The motion of the gear produces a phase-shifted 4130 G field at E1 and E2 (Figure 3 (a)); internal 150 G conditioning circuitry subtracts the field at the B = +25 G two elements (Figure 3 (b)); and the Schmitt OP (b) trigger at the output of the conditioning B – B 0 G E1 E2 circuitry switches at the pre-determined B = –25 G RP thresholds (B and B ). As shown (Figure OP RP -150 G 3 (c)), the IC output is LOW whenever sensor E1 sees a (ferrous) gear tooth and sensor E2 faces air. The output is HIGH when sensor V OUT (c) E1 sees air and sensor E2 sees the ferrous V OUT(SAT) target. OUTPUT DUTY CYCLE ≈ 50% Dwg. WH-003 A gear-tooth sensor can be configured (see ASSEMBLY TECHNIQUES) to operate as a latch, a (positive) switch, or a negative switch. Note the change in duty cycle in each of the cases (Figure 4). In the configuration shown in Figure 3, such a device will switch ON and then switch OFF on the leading or rising edge of the target tooth A latch is a device where the operate (Figure 4 (a)). point is greater than zero gauss and the release point is less than zero gauss. With A negative switch is a device where both the operate and release the configuration shown in Figure 3, such a points are less than zero gauss (negative values). In the configuration device will switch ON on the leading edge shown in Figure 3, such a device will switch OFF and then switch ON and OFF on the trailing edge of the target on the trailing or falling edge of the target tooth (Figure 4 (b)). tooth. Speed sensors can use any of the three sensor configurations A (positive) switch is a device where described. Timing sensors, however, must use a latch to guarantee both the operate and release points are dual-edge detection. Latches are most easily made using the greater than zero gauss (positive values). A3058EU or A3058LU device types. www.allegromicro.com 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED SYSTEM ISSUES Figure 4 Optimal performance of a gear-tooth POSITIVE AND NEGATIVE SWITCH OPERATION sensing system strongly depends on four 150 G factors: the IC magnetic parameters, the B = +100 G magnet, the pole piece configuration, and OP B = +50 G RP the target. B – B E1 E2 Sensor Specifications. Shown in Figure 5 are graphs of the differential field as -150 G (a) a function of air gap. A 48-tooth, 2.5” (63.5 mm) diameter, uniform wheel similar to V that used in ABS applications is used. The OUT samarium cobalt magnet is 0.32” diameter by V OUT(SAT) 0.20” long (8.13 x 5.08 mm). The maximum OUTPUT DUTY CYCLE = 65% functioning air gap with this typical gear/ magnet combination can be determined 150 G using the graphs and the specifications for the sensor IC. B – B E1 E2 In this case, if an A3056EU/LU sensor B = -50 G OP with a B of +25 G and a B of -25 G is OP RP B = -100 G RP used, the maximum allowable air gap would -150 G (b) be 0.110” (2.79 mm). If the switch points change +75 G with temperature (B = + 100 OP G, B = +50 G), the maximum air gap will be V RP OUT approximately 0.077” (1.96 mm). V OUT(SAT) OUTPUT DUTY CYCLE = 33% All system issues should be translated Dwg. WH-004 back to such a profile to aid the prediction of system performance. Magnet Selection. These devices can +150°C it may irreversibly lose magnetic strength. Of these three be used with a wide variety of commercially magnet materials, Alnico-8 is the least expensive by volume and available permanent magnets. The selection SmCo is the most expensive. of the magnet depends on the operational and environmental requirements of the Either cylindrical- or cube-shaped magnets can be used, as long sensing system. For systems that require as the magnet pole face at least equals the facing surface(s) of the IC high accuracy and large working airgaps or package and the pole piece. Choose the length of the magnet to an extended temperature range, the usual obtain a high length-to-width ratio, up to 0.75:1 for rare earths, or 1.5:1 magnet material of choice is rare earth for Alnico-8. Any added magnet length may incrementally improve the samarium cobalt (SmCo). This magnet allowable maximum air gap. material has a high energy product and can operate over an extended temperature range. Magnets, in general, have a non-uniform magnetic surface profile. For systems that require low-cost solutions The flux across the face of a magnet can vary by as much as 5% of the for an extended temperature range, Alnico-8 average field over a 0.10” (2.5 mm) region. If a Hall sensor is placed can be used. Due to its relatively low energy directly on a magnet face, the non-uniformity can appear to shift the product, smaller operational airgaps can be operating parameters of the sensor. For example, if a device is placed expected. At this time, neodymium iron on a 3000 G magnet with ±2% face offsets, each of the operating boron (NeFeB) is not a proven high-tempera- points might be shifted by ±60 G. When offsets are present, the ture performer; at temperatures above operating characteristics may be greatly altered. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED Figure 5 Pole Piece Design. A pole piece may be used at the face of the magnet to smooth out the magnet-face offsets. A 0.020” (0.51 mm) DIFFERENTIAL FLUX DENSITY thick, soft-iron pole piece will bring the field non-uniformity down to 2000 the ±1%-to-±3% range. Note that pole pieces will minimize but not 1500 eliminate the non-uniformity in the magnet face field. Front pole pieces will almost always result in a reduced maximum air gap. 1000 500 Ferrous Targets. The best ferrous targets are made of cold-rolled low-carbon steel. Sintered-metal targets are also usable, but care 0 must be taken to ensure uniform material composition and density. -500 The teeth or slots of the target should be cut with a slight angle -1000 so as to minimize the abruptness of transition from metal to air as the target passes by the sensor. Sharp transitions will result in magnetic -1500 overshoots that can result in false triggering. -2000 0 0.025 0.050 0.075 0.100 0.125 AIRGAP FROM PACKAGE FACE IN INCHES Gear teeth larger than 0.10” (2.54 mm) wide and at least 0.10” Dwg. GH-035 (2.54 mm) deep provide reasonable working air gaps and adequate 200 change in magnetic field for reliable switching. Generally, larger teeth and slots allow a larger air gap. A gear tooth width approximating the 150 spacing between sensors (0.088” or 2.24 mm) requires special care in 100 the system design and assembly techniques. 50 ASSEMBLY TECHNIQUES 0 Due to magnet face non-uniformities and device variations, it is -50 recommended that applications requiring precision switching utilize a mechanical optimization procedure during assembly. Without a pole -100 piece, the inherent magnet face offsets can be used to pre-bias the -150 magnetic circuit to obtain any desired operating mode. This is achieved by physically changing the relative position of the magnet -200 0.070 0.080 0.090 0.100 0.110 0.120 behind the sensor to achieve the desired system performance objec- AIRGAP FROM PACKAGE FACE IN INCHES Dwg. GH-036 tive. For example, with a rotating ABS gear, the objective might be a 50% duty cycle at maximum air gap. Similar objectives can be set for ignition (crank and cam position) sensing systems. SENSOR LOCATIONS (±0.005” [0.13 mm] die placement) Non-precision speed sensing applications do not require optimiza- tion. For applications where mechanical optimization is not feasible, ACTIVE AREA DEPTH 0.015" non-zero speed devices such as the UGN/UGS3059KA ac-coupled 0.088" 0.38 mm 2.23 mm gear-tooth sensor are available. NOM 0.075" 1.89 mm E1 E2 A BRANDED SURFACE 1 2 3 Dwg. MH-002-8D www.allegromicro.com DIFFERENTIAL FLUX DENSITY IN GAUSS DIFFERENTIAL FLUX DENSITY IN GAUSS 0.046" 1.17 mm 3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS –ZERO SPEED Dimensions in Inches Dimensions in Millimeters (controlling dimensions) (for reference only) 0.183 4.65 0.178 4.52 0.063 1.60 0.059 1.50 0.181 4.60 0.176 4.47 45° 45° 0.018 0.46 0.086 2.18 1 2 3 1 2 3 MAX MAX 0.0173 15.24 0.44 0.600 14.23 0.35 0.560 0.0138 0.48 0.0189 0.0142 0.36 SEE NOTE SEE NOTE 1.27 0.050 2.54 0.100 Dwg. MH-003E mm Dwg. MH-003E in 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; NOTES:1. Tolerances on package height and width represent 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents allowable mold offsets. Dimensions given are pending. measured at the widest point (parting line). Allegro MicroSystems, Inc. reserves the right to make, from time to 2. Exact body and lead configuration at vendor’s option time, such departures from the detail specifications as may be within limits shown. required to permit improvements in the performance, reliability, or 3. Height does not include mold gate flash. manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. 4. Recommended minimum PWB hole diameter to Allegro products are not authorized for use as critical components clear transition area is 0.035” (0.89 mm). in life-support appliances, devices, or systems without express written 5. Where no tolerance is specified, dimension is approval. nominal. The information included herein is believed to be accurate and 6. Minimum lead length was 0.500” (12.70 mm). If reliable. However, Allegro MicroSystems, Inc. assumes no responsi- existing product to the original specifications is not bility for its use; nor for any infringements of patents or other rights of acceptable, contact sales office before ordering. third parties that may result from its use. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000