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3064
HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
The A3064LKA ac-coupled Hall-effect gear-tooth sensor is a monolithic integrated circuit that switches in response to changing differential magnetic fields created by moving ferrous targets. This device is ideal for use in non-zero-speed, gear-tooth-based speed, position, and timing applications such as in anti-lock braking systems, transmissions, and crankshafts. When coupled with a back-biasing magnet, the sensor can be configured to turn on or off with the leading or trailing edge of a geartooth or slot. Changes in fields on the magnet face caused by a moving ferrous mass are sensed by two integrated Hall transducers and are differentially amplified by on-chip electronics. This differential sensing design provides immunity to radial vibration within the device's operating air gap. Steady-state magnet and system offsets are eliminated using an on-chip differential band-pass filter. This filter also provides relative immunity to interference from RF and electromagnetic sources. The on-chip temperature compensation and Schmitt trigger circuitry minimizes shifts in effective working air gaps and switch points over temperature, allowing operation to low frequencies over a wide range of air gaps and temperatures. Each Hall-effect digital Integrated circuit includes a voltage regulator, two quadratic Hall-effect sensing elements, temperature compensating circuitry, a low-level amplifier, band-pass filter, 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 easily switch 20 mA over the full frequency response range of the sensor and is compatible with bipolar and MOS logic circuits. The device is packaged in a 5-pin plastic SIP.
Data Sheet 27612.21
X
X
VCC
1
2
3
4
5
GROUND
FILTER
SUPPLY
OUTPUT
Dwg. PH-011-1
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
at TA = +25C
Supply Voltage, VCC ............................. 24 V Reverse Battery Voltage, VRCC .......... -30 V Magnetic Flux Density, B ............ Unlimited Output Off Voltage, VOUT ...................... 24 V Output Current, IOUT ......................... 25 mA Package Power Dissipation, PD ............................................ 500 mW Operating Temperature Range, TA ............................... -40C to +150C Storage Temperature Range, TS ............................... -65C to +170C
FILTER
FEATURES
s s s s s s s s s
Senses Motion of Ferrous Targets Wide Operating Temperature Range Operation to 30 kHz Resistant to EMI Large Effective Air Gap 4.5 V to 24 V Operation Output Compatible With All Logic Families Reverse Battery Protection Resistant to Physical Stress
Always order by complete part number, e.g., A3064LKA .
3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
1 SUPPLY
FUNCTIONAL BLOCK DIAGRAM
REG
OUTPUT 2
+ X X
4 FILTER 5 FILTER
3 GROUND
Dwg. FH-008-1
ELECTRICAL CHARACTERISTICS over operating temperature and supply voltage range.
Limits Characteristic Supply Voltage Output Saturation Voltage Output Leakage Current Supply Current Symbol VCC VOUT(SAT) IOFF ICC fcoh tr tf Test Conditions Operating IOUT = 18 mA, B < BRP VOUT = 24 V, B > BOP B < BRP B > BOP High-Frequency Cutoff Output Rise time Output Fall time -3 dB VOUT = 12 V, RL = 820 VOUT = 12 V, RL = 820 Min. 4.5 -- -- -- -- 30 -- -- Typ. -- 141 -- 11 9.6 -- 0.04 0.18 Max. 24 400 5.0 20 -- -- 0.2 0.3 Units V mV A mA mA kHz s s
MAGNETIC CHARACTERISTICS over operating temperature and supply voltage range.
Limits Characteristic Operate Point Release Point Hysteresis Symbol BOP BRP Bhys Test Conditions Output switches on to off Output switches off to on BOP - BRP Min. 0 -12.5 5.0 Typ. 15 0 15 Max. 27.5 7.5 35 Units G G G
NOTES: 1. Magnetic switch points are specified as the difference in magnetic fields at the two Hall elements. 2. As used here, negative flux densities are defined as less than zero (algebraic convention). 3. Typical values are at TA = 25C and VCC = 12 V. 4. 1 gauss (G) is exactly equal to 0.1 millitesla (mT).
2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 2001 Allegro MicroSystems, Inc.
3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
TYPICAL OPERATING CHARACTERISTICS
SWITCH POINTS
30
V CC= 12 V
DIFFERENTIAL FLUX DENSITY IN GAUSS
20
OPERATE POINT
10
0
RELEASE POINT
-10 -50 -25 0 25 50 75 100 125 150 AMBIENT TEMPERATURE IN C
Dwg. GH-056-1
OUTPUT SATURATION VOLTAGE
300
200
I OUT = 18 mA V CC = 12 V
I OUT = 18 mA TA= +25C
SATURATION VOLTAGE IN mV
200
SATURATION VOLTAGE IN mV
150
100
100
0 -50
50
-25
0
25
50
75
100
125
150
0
5
10
15
20
25
AMBIENT TEMPERATURE IN C
Dwg. GH-029-6
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-055-2
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3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
TYPICAL OPERATING CHARACTERISTICS
SUPPLY CURRENT
20
VCC = 24 V
20
15
15
SUPPLY CURRENT IN mA
SUPPLY CURRENT IN mA
B < B RP
B < B RP
10
B > B OP
10
B > B OP
5
5
TA = +25C
0 -50
0
-25 0 25 50 75 100 125 150
0
5
10
15
20
25
AMBIENT TEMPERATURE IN C
Dwg. GH-028-9
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-031-3
APPLICATIONS INFORMATION
The A3064LKA is a versatile high-precision differential sensing device that can be used in a wide range of applications. Careful choice of the sensor IC, target material and shape, magnet material and shape, and assembly techniques enables large working air gaps and high switch-point accuracy over the system operating temperature range. Magnet Biasing. To sense moving non-magnetized ferrous targets, these devices must be back biased by mounting the unbranded side on a small permanent magnet. Either magnetic pole (north or south) can be used. The devices can be used without a back-biasing magnet. For example, the sensor can be used to detect a rotating ring magnet such as those found in brushless dc motors or in speed sensing applications. Sensor Operation. These sensor ICs each contain two integrated Hall transducers (E1 and E2) that are used to sense a magnetic field differential across the face of the IC (see Sensor Location drawing). Referring to the Typical Transfer Characteristic (Figure 1), the trigger switches the output off (output high) when BE1 - BE2 > BOP and switches the output on (output Figure 1 TYPICAL TRANSFER CHARACTERISTIC
+V
V CC
OUTPUT VOLTAGE
B RP
BOP
VOUT(SAT)
0 -B
0 FLUX DENSITY
+B
Dwg. GH-007-6
4
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
APPLICATIONS INFORMATION (cont'd)
low) when BE1 - BE2 < BRP. The difference between BOP and BRP is the hysteresis of the device. Note that powering up in the absence of a differential magnetic field (less than the device BOP and higher than the device BRP) will allow an indeterminate output state. The correct output state is warranted after the first excursion beyond BOP or BRP. Figure 2 relates the output state of a back-biased sensor IC, with switching characteristics shown in Figure 1, to the target gear profile and position. Assume a north pole back-bias configuration (equivalent to a south pole at the face of the device). The motion of the gear produces a phase-shifted field at E1 and E2 (Figure 2(a)); internal conditioning circuitry subtracts the fields at the two elements (Figure 2(b)); this differential field is band-pass filtered to remove dc offset components and then fed into a Schmitt trigger; the Schmitt trigger switches the output transistor at the thresholds BOP and BRP. As shown (Figure 2(c)), the IC output is low whenever sensor E2 faces a (ferrous) gear tooth and sensor E1 faces air. The output is high when sensor E1 faces air and sensor E2 faces a ferrous target. AC-Coupled Operation. Steady-state magnet and system offsets are eliminated using an on-chip differential bandpass filter. The lower frequency cut-off of this patented filter is set using an external capacitor, the value of which can range from 0.01 F to 10 F. The high-frequency cut-off of this filter is set at 30 kHz by an internal integrated capacitor. The differential structure of this filter improves the ability of the IC to reject single-ended noise on the ground or supply line and, as a result, makes it more resistant to radio-frequency and electromagnetic interference typically seen in hostile remote-sensing environments. This filter configuration also increases system tolerance to capacitor degradation at high temperatures, allowing the use of an inexpensive external ceramic capacitor. Low-Frequency Operation. Low-frequency operation of the sensor is set by the value of an external capacitor. Ideally, the differential flux density range (determined by the applied target) vs. air gap assumes a perfect sinusoidal input. Figure 3 provides the low-frequency cut-off (-3 dB point) of the filter as a function of capacitance value. This information should be used with care. In reality, when used with gear teeth,
4300 G
Figure 2
LEADING EDGE TRAILING EDGE
GEAR
DIRECTION OF ROTATION
E2 NORTH
E1
SOUTH
B &B
E1
E2
(a)
4150 G 150 G BOP= +15 G
(b)
B -B
E1 E2
0G B RP= 0 G
-150 G
V
OUT
(c)
V
OUT(SAT)
OUTPUT DUTY CYCLE 50%
Dwg. WH-003-3
Figure 3
1k
100
LOW-FREQUENCY CUTOFF IN Hz
10
1.0
0.1 0.01 0.1 1.0 10
CAPACITANCE IN F
Dwg. GH-025
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3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
APPLICATIONS INFORMATION (cont'd)
the teeth create transitions in the magnetic field that have a much higher frequency content than the basic rotational speed of the target. This allows the device to sense speeds much lower than those indicated by the graph for a given capacitor value. Capacitor Characteristics. The major requirement for the external capacitor is its ability to operate in a bipolar (nonpolarized) mode. Another important requirement is the low leakage current of the capacitor (equivalent parallel resistance should be greater than 500 k). To maintain proper operation with frequency, capacitor values should be held to within 30% over the operating temperature range. The commonly available Z5U ceramic capacitor temperature code should not be used in this application. Magnet Selection. The A3064LKA can be used with a wide variety of commercially available permanent magnets. The selection of the magnet depends on the operational and environmental requirements of the sensing system. For systems that require high accuracy and large working air gaps or an extended temperature range, the usual magnet material of choice is rare-earth samarium cobalt (SmCo). This magnet material has a high energy product and can operate over an extended temperature range. For systems that require low-cost solutions for an extended temperature range, AlNiCo 8 can be used. Due to its relatively low energy product, smaller operational air gaps can be expected. Neodymium iron boron (NeFeB) can be used over moderate temperature ranges when large working air gaps are required. Of these three magnet materials, AlNiCo 8 is the least expensive by volume and SmCo is the most expensive. Extensive applications information for Hall-effect sensors is available in: * Hall-Effect IC Applications Guide, Application Note 27701; * Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and Lead Forming, Application Note 27703.1; * Soldering of Through-Hole Hall-Sensor Dervices, Application Note 27703; and * Soldering of Surface-Mount Hall-Sensor Devices, Application Note 27703.2. All are provided in Allegro Electronic Data Book, AMS-702. or at
BRANDED SURFACE
Figure 4 SENSOR LOCATIONS (0.005 [0.13 mm] die placement)
ACTIVE AREA DEPTH 0.0165" 0.42 mm NOM 0.087" 2.20 mm 0.083" 2.10 mm
0.075" 1.91 mm
E1
E2
A
1 2 3 4 5
Dwg. MH-007E
Allegro
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6
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
CRITERIA FOR DEVICE QUALIFICATION
All Allegro sensors are subjected to stringent qualification requirements prior to being released to production. To become qualified, except for the destructive ESD tests, no failures are permitted.
Qualification Test Biased Humidity (HAST) Test Method and Test Conditions JESD22-A101, RH = 85% Test Length 2000 hrs Samples 320 Comments VCC = VOUT = 12 V 116 pcs at TA = 25C 116 pcs at TA = 150C VCC = VOUT = 12 V 116 pcs at TA = 25C 30 pcs at TA = 150C VCC = VOUT = 7.5 V
High-Temperature Operating Life (HTOL)
JESD22-A108, TJ 190C TA = 175C, TJ 190C JESD22-A102, Condition C, TA = 121C at 15 psig
2000 hrs
146
Accelerated HTOL Autoclave, Unbiased
500 hrs 192 hrs
50 77
Solder Heat High-Temperature (Bake) Storage Life Temperature Cycle (unbiased) ESD, Human Body Model MIL-STD-883, Method 1008, TA = 170C MIL-STD-883, Method 1010, +25C to +150C MIL-STD-883, Method 3015 2000 hrs
22 77
2000 cycles
153
Pre/Post Reading
3 per test
Test to failure, All leads > 2 kV
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; 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 appliances, 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 infringements of patents or other rights of third parties that may result from its use.
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3064 HALL-EFFECT GEAR-TOOTH SENSOR --AC COUPLED
Dimensions in Inches
(controlling dimensions)
0.252 0.247
Dimensions in Millimeters
(for reference only)
6.40 6.27
0.063 0.059
1.60 1.50
0.181 0.176 45 0.018
4.60 4.47 45 0.46
0.083
MAX
1
2
3
4
5
2.11
MAX
1
2
3
4
5
0.600 0.560
0.0173 0.0138
15.24 14.23
0.44 0.35
SEE NOTE
SEE NOTE
0.0189 0.0142
0.050
BSC
Dwg. MH-010H in
0.48 0.36
1.27
BSC
Dwg. MH-010H mm
Surface-Mount Lead Form (order A3064LKA-TL)
0.095
0.005
2.41
0.13
0.002
MAX
0.051
MAX
0.004 0-8
MAX
0.020
MIN FLAT
Dwg. MH-015 in
0.10
MAX
0-8 0.51
MIN FLAT
Dwg. MH-015 mm
NOTES:
1. 2. 3. 4. 5. 6.
Tolerances on package height and width represent allowable mold offsets. Dimensions given are measured at the widest point (parting line). Exact body and lead configuration at vendor s option within limits shown. Height does not include mold gate flash. Recommended minimum PWB hole diameter to clear transition area is 0.035 (0.89 mm). Where no tolerance is specified, dimension is nominal. Supplied in bulk pack (500 pieces per bag).
8
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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