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Part: 3056
Category:
Sensors
-> Hall Effect Sensors
Description: Hall Effect Gear-tooth Sensors-zero Speed
Company: Allegro Micro Systems, Inc.
Datasheet: Download 3056 datasheet File size : 2164 kB
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3046, 3056, AND 3058
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, and timing applications and operate down to zero rpm over a wide range of air gaps and temperatures. When combined with a backbiasing 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.
HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED
Data Sheet 27612A
X
X
V
CC
1
2
3
GROUND
OUTPUT
SUPPLY
The six devices differ only in their magnetic switching values and 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 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.
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BENEFITS
s s s s s s s s s Senses Ferrous Targets Down to Zero RPM Large Effective Air Gap Wide Operating Temperature Range Operation from Unregulated Supply High-Speed Operation Output Compatible With All Logic Families Reverse Battery Protection Solid-State Reliability Resistant to Physical Stress
Dwg. PH-012
Pinning is shown viewed from branded side.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC . . . . . . . . . . . . . . 28 V Reverse Battery Voltage, V RCC . . . . . . . . . . . . . . . . . . . . . . -30 V
Magnetic Flux Density, B . . . . . Unlimited Output OFF Voltage, VOUT . . . . . . . . . 28 V Reverse Output Voltage, VOUT . . . . . -0.5 V Output Current, IOUT . . . . . . . . . . . . 25 mA Package Power Dissipation, PD . . 500 mW Operating Temperature Range, TA Suffix "EU" . . . . . . . . . -40°C to +85°C Suffix "LU" . . . . . . . . -40°C to +150°C Storage Temperature Range, TS . . . . . . . . . . . . . . . -65°C to +170°C
The A3046xU is not for new design.
Switching Hysteresis 15-90 G Operating Temp. Range -40°C to +85°C -40°C to +150°C A3046EU A3056EU A3046LU A3056LU 150-250 G A3058EU A3058LU Device Type Number
3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED
All devices, when used with a backbiasing magnet, can be configured to turn ON or OFF with the leading or trailing edge of a gear tooth 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. The on-chip temperature compensation and Schmitt trigger circuitry minimizes shifts in effective working air gaps and switch points over temperature making these devices ideal for use in ignition timing, anti-lock braking systems, and speed measurement systems in hostile automotive and industrial environments. Each Hall effect digital Integrated circuit includes two quadratic Hall effect sensing elements, a voltage regulator, temperature 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 mA at conservatively specified repetition rates to 20 kHz and is compatible with bipolar and MOS logic circuits.
FUNCTIONAL BLOCK DIAGRAM
1 SUPPLY
REG
OUTPUT 3
+ X X
2 GROUND
Dwg. FH-010
Both magnetic characteristics are available in a choice of two operating temperature ranges. Suffix EU devices have an operating range of -40°C to +85°C while suffix LU devices feature an operating range of -40°C to +150°C. All devices are packaged in a 3-pin plastic SIP.
ELECTRICAL CHARACTERISTICS at VCC = 8 V, over operating temperature range.
Limits Characteristic Supply Voltage Power-Up State Output Saturation Voltage Output Leakage Current Supply Current Output Rise time Output Fall time Symbol VCC -- VOUT(SAT) IO F F IC C tr tf Test Conditions Operating 3058* only, VCC = 0 4.5 V, B BOP VCC = VOUT = 24 V, B < BRP VCC = 24 V, B < BRP RL = 820 , CL = 20 pF RL = 820 , CL = 20 pF -- -- -- -- -- Min. 4.5 Typ. -- Output is OFF 135 -- 7.2 100 100 400 5.0 14 -- -- Max. 24 Units V -- mV µA mA ns ns
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 VCC = 8 V.
Part Numbers* 3046 Characteristic Operate Point, BOP Test Conditions Output Switches OFF to ON, TA = +25°C Output Switches ON to OFF, TA = +25°C BOP-BRP, TA = +25°C Over operating temperature range, Ref. BOP or BRP at TA = +25°C Min. Typ. Max. -- -- 150 3056 Min. Typ. Max. -- -- 150 3058 Min. Typ. Max. -- -- 250
Release Point, BRP
-150
--
--
-150
--
--
-250
--
--
H y s t e r e s i s , B hys
15
50
90
15
50
90
150 200 250
Change in Trip Point, BOP or BRP
--
--
± 50
--
--
± 75
--
--
± 50
SATURATION VOLTAGE IN mV
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 = +25°C. * Complete part number includes the prefix `A' and a suffix to identify operating temperature range and package style. See selection guide.
TYPICAL OPERATING CHARACTERISTICS
200
V =8V CC I OUT 20 mA =
180
160
140
120
100 -50 0 50 100 150
Dwg. GH-033
AMBIENT TEMPERATURE IN °C
10
TA = +25°C
11
V CC= 24 V
10
9
SUPPLY CURRENT IN mA
B > BOP
SUPPLY CURRENT IN mA
9
B > B OP
8
B < BRP
8
7
7
B < BRP
6
6
5 0 5 10 15 20 25
Dwg. GH-031
5 -50
0
50
100
150
Dwg. GH-032
SUPPLY VOLTAGE IN VOLTS
AMBIENT TEMPERATURE IN °C
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3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED
Figure 1
APPLICATIONS INFORMATION
A gear-tooth sensing system consists of the sensor IC, a backbiasing 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 speed ranges, minimum pulse duration or duty cycle, and switch point accuracy. Careful choice of the sensor IC, magnet material and shape, target material and shape, and assembly techniques enables large working air gaps and high switch-point accuracy over the system operating temperature range. Naming Conventions. With a south pole in front of the branded 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 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 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 magnet such as those found in brushless dc motors or in speed sensing applications. Here, the sensor detects the magnetic field gradient created by the magnetic poles. Figure 2
TYPICAL GEAR-TOOTH SENSING APPLICATION
BACK-BIASING MAGNET S
OPTIONAL POLE PIECE
SENSOR IC
A
N
S
TARGET GEAR
TYPICAL TRANSFER CHARACTERISTIC
Dwg. AH-003
24 V MAX
OUTPUT VOLTAGE IN VOLTS
B OP
B RP
0 -B
V OUT(SAT)
0 DIFFERENTIAL FLUX DENSITY, BE1 BE2
+B
Dwg. GH-034
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3046, 3056, AND 3058 HALL EFFECT GEAR-TOOTH SENSORS ZERO SPEED
Sensor Operation. The A3046EU/LU, A3056EU/LU, and A3058EU/LU 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 Figure 2, the trigger switches the output ON (output LOW) when BE1 BE2 > BOP and switches the output OFF (output HIGH) when BE1 BE2 < BRP. The difference between BOP and BRP is the hysteresis of the device. Figure 3 relates the output state of a back-biased sensor IC, with switching characteristics shown in Figure 2, to the target gear profile and position. Assume a north pole back-bias configuration (equivalent to south pole at the face of the device). The motion of the gear produces a phase-shifted field at E1 and E2 (Figure 3 (a)); internal conditioning circuitry subtracts the field at the two elements (Figure 3 (b)); and the Schmitt trigger at the output of the conditioning circuitry switches at the pre-determined thresholds (BOP and BRP). As shown (Figure 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 E1 sees air and sensor E2 sees the ferrous target. 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). A latch is a device where the operate point is greater than zero gauss and the release point is less than zero gauss. With the configuration shown in Figure 3, such a device will switch ON on the leading edge and OFF on the trailing edge of the target tooth. A (positive) switch is a device where both the operate and release points are greater than zero gauss (positive values).
Figure 3
GEAR-TOOTH SENSOR OPERATION
LEADING EDGE TRAILING EDGE
GEAR
DIRECTION OF ROTATION
E2
E1 NORTH SOUTH
4300 G
B &B
E1
E2
(a)
4130 G 150 G B OP= +25 G
(b)
B B
E1 E2
0G B RP= 25 G -150 G
V
OUT
(c)
V
OUT(SAT)
OUTPUT DUTY CYCLE 50%
Dwg. WH-003
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 (Figure 4 (a)). A negative switch is a device where both the operate and release points are less than zero gauss (negative values). In the configuration shown in Figure 3, such a device will switch OFF and then switch ON on the trailing or falling edge of the target tooth (Figure 4 (b)). Speed sensors can use any of the three sensor configurations described. Timing sensors, however, must use a latch to guarantee dual-edge detection. Latches are most easily made using the A3058EU or A3058LU device types.
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