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3425
DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
The A3425LK dual Hall-effect switch is an extremely temperature-stable and stress-resistant sensor especially suited for use in digital-encoder systems in the harsh environments of automotive or industrial applications over extended temperature ranges to +150C. Superior high-temperature performance is made possible through dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. This device also eliminates the major manufacturing hurdles encountered in fine-pitch direction-detection applications, namely maintaining accurate mechanical location between the two active Hall elements. Here, the two Hall elements are photolithographically aligned to better than 1 m, as contrasted with 100 m or worse mechanical location tolerance when manufactured discretely. The A3425LK is an ultra-sensitive device optimized for use with highdensity ring magnets. The device includes on a single silicon chip a voltage regulator, two independent chopper-stabilized Hall-voltage generators , two smallsignal amplifiers, two Schmitt triggers, and two short-circuit protected open-collector outputs to sink up to 30 mA each. An on-board regulator permits operation with supply voltages of 3.3 to 26.5 volts. With suitable output pull ups, it can be used directly with bipolar or MOS logic circuits. The A3425LK dual Hall-effect switch is supplied in a 4-pin plastic SIP for operation over a temperature range of -40C to +150C. A similar device, with on-chip logic processing specifically for direction detection applications, in a 5-pin SIP, is the A3422LKA.
Data Sheet 27651.20
X
V CC
1
2
3
X
4
OUTPUT2
Dwg. PH-017
OUTPUT1
Pinning is shown viewed from branded side.
PRELIMINARY INFORMATION
(subject to change without notice) August 21, 2000 ABSOLUTE MAXIMUM RATINGS
at TA = +25C Supply Voltage, VCC ........................ 26.5 V Reverse Battery Voltage, VRCC .......... -18 V Zener Current, IZ ............................ 100 mA Magnetic Flux Density, B ........... Unlimited Output Off Voltage, VOUT .................... VCC Output Current, IOUT ........................ 30 mA Reverse Output Current, IOUT ........ -50 mA Package Power Dissipation, PD . See Graph Junction Temperature, TJ ............... +170C Operating Temperature Range, TA, ............................ -40C to +150C Storage Temperature Range, TS .............................. -65C to +170C
GROUND
SUPPLY
FEATURES
I Two Matched Hall Switches On A Single Substrate
I I I I I I I I
1 mm Sensor-to-Sensor Spacing Superior Temperature Stability Resistant to Physical Stress Output Short-Circuit Protection Operation From Unregulated Supply Reverse Battery Protection Solid-State Reliability Integrated ESD Protection on Outputs and Supply
Always order by complete part number, e.g., A3425LK .
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
FUNCTIONAL BLOCK DIAGRAM
1 SUPPLY
REG.
TO ALL SUBCIRCUITS
E1
DYNAMIC OFFSET CANCELLATION
OUTPUT1
LOW-PASS FILTER SAMPLE & HOLD
X
2 CONTROL
CURRENT LIMIT <1
E2
DYNAMIC OFFSET CANCELLATION
OUTPUT2
LOW-PASS FILTER SAMPLE & HOLD
X
3 CONTROL
CURRENT LIMIT <1 GROUND 4
Dwg. FH-020-7
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
1.0
0.8
0.6
0.4
FREE AIR, R JA = 177C/W
0.2
0 -25
0
25
50
75
100
125
150
175
AMBIENT TEMPERATURE IN C
Dwg. GH-001-1
2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 2000, Allegro MicroSystems, Inc.
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
ELECTRICAL CHARACTERISTICS over operating temperature range, each switch tested separately (unless otherwise specified).
Limits Characteristic Supply Voltage Range Output Leakage Current Output Saturation Voltage Output Current Limit Chopping Frequency Output Rise Time Output Fall Time Total Supply Current Symbol VCC IOFF VOUT(SAT) IOM fC tr tf ICC RL = 820 , CL = 10 pF RL = 820 , CL = 10 pF Both outputs off, VCC 26.5 V Both outputs on, VCC 26.5 V Reverse Battery Current Zener Voltage Zener Impedance ICC VZ + VD zz + z D VRCC = -18 V ICC = 15 mA, TA = 25C ICC = 15 mA, TA = 25C Test Conditions Operating, TJ < 170C1 VOUT = 18 V, B < BRP IOUT = 20 mA, B > BOP B > BOP Min. 3.3 - - 30 - - - - - - 28 - Typ. - <1.0 225 - 340 110 55 3.8 7.5 2.0 33 50 Max. 26.5 10 400 55 - - - 6.0 10 15 37 100 Units V A mV mA kHz ns ns mA mA mA V
NOTES:1. Supply voltage is limited by allowable package power dissipation as a function of ambient temperature. 2. BOP = operate point (output turns on); BRP = release point (output turns off). 3. Typical Data is at TA = +25C and VCC = 12 V and is for design information only.
MAGNETIC CHARACTERISTICS over operating supply voltage and temperature ranges, each switch tested separately (unless otherwise specified).
Limits Characteristic Operate Point Symbol BOP1 BOP2 Release Point BRP1 BRP2 Hysteresis Operate Differential Release Differential Symmetry Bhys BOP(dif) BRP(dif) Bsym BOP - BRP BOP1 - BOP2 BRP1 - BRP2 BOP + BRP Test Conditions Min. - - -24 -24 5.0 - - - Typ. 8.0 11 -11 -8.0 19 -2.0 -3.3 - Max. 24 24 - - 35 30 30 30 Units G G G G G G G G
NOTES:1. As used here, negative flux densities are defined as less than zero (algebraic convention) and -50 G is less than +10 G. 2. Typical Data is at TA = +25C and VCC = 12 V and is for design information only.
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3
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
TYPICAL OPERATING CHARACTERISTICS as a function of temperature
CHANNEL 1 SWITCH POINTS
25 20 15
CHANNEL 2 SWITCH POINTS
25 20 15 VCC = 26.5 V VCC = 18 V VCC = 3.3-5 V
SWITCH POINT IN GAUSS
SWITCH POINT IN GAUSS
10 5 0 -5 -10 -15 -20 -25 -50 OPERATE POINT
VCC = 18-26.5 V VCC = 3.3-5 V
10 OPERATE POINT 5 0 -5 -10 -15 -20 RELEASE POINT VCC = 26.5 V VCC = 5 V VCC = 18 V VCC = 3.3 V
VCC = 5 V VCC = 3.3 V VCC = 18 V VCC = 26.5 V
RELEASE POINT
-25
0
25
50
75
100
125
150
-25 -50
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN C
Dwg. GH-026-7
AMBIENT TEMPERATURE IN C
Dwg. GH-026-8
OUTPUT SATURATION VOLTAGE
300
TOTAL SUPPLY CURRENT
8
VCC = 3.3 V
SATURATION VOLTAGE IN mV
B BOP
VCC = 18 V
VCC = 26.5 V
SUPPLY CURRENT IN mA
VCC = 3.3 V 6
200
4
B BRP VCC = 3.3 V
VCC = 18 V
100 IOUT = 20 mA
2
0 -50
-25
0
25
50
75
100
125
150
0 -50
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN C
Dwg. GH-029-5
AMBIENT TEMPERATURE IN C
Dwg. GH-028-8
4
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
TYPICAL OPERATING CHARACTERISTICS (cont'd) as a function of supply voltage
OPERATE AND RELEASE DIFFERENTIALS
25 20 15
BOP/BRP DIFFERENTIAL IN GAUSS
10 5 0 -5 -10 -15 -20 -25 -50 BRP VCC = 3.3 V VCC = 5 V VCC = 18 V BOP VCC = 3.3 V VCC = 5-18 V
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN C
Dwg. GH-026-9
ACTIVE AREA DEPTH 0.015" 0.38 mm NOM
0.039" 1.00 mm
0.083" 2.11 mm
0.053" 1.34 mm E1 E2
SENSOR LOCATIONS
(0.005" [0.13 mm] die placement)
BRANDED SURFACE
A
1 2 3 4
Allegro
Dwg. MH-001-4
Although sensor location is accurate to three sigma for a particular design, product improvements may result in small changes to sensor location.
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5
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
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, TA = 85C, RH = 85% JESD22-A108, TA = 150C, TJ = 165C TA = 170C, TJ = 180C Test Length 1000 hrs Samples 77 Comments VCC = VOUT = 3.3 V
High-Temperature Operating Life (HTOL) Accelerated HTOL
1000 hrs
77
168 hrs
77
Autoclave, Unbiased High-Temperature (Bake) Storage Life Temperature Cycle
JESD22-A102, Condition C, MIL-STD-883, Method 1008, TA = 170C MIL-STD-883, Method 1010, -55C to +150C CDF-AEC-Q100-002
96 hrs 1000 hrs
77 77
1000 cycles
77
ESD, Human Body Model
Pre/Post Reading
x per test
Test to failure, All leads > TBD
6
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
FUNCTIONAL DESCRIPTION
Chopper-Stabilized Technique. These devices use a proprietary dynamic offset cancellation technique, with an internal high-frequency clock to reduce the residual offset voltage of the Hall element that is normally caused by device overmolding, temperature dependencies, and thermal stress. This technique produces devices that have an extremely stable quiescent Hall output voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. This technique will also slightly degrade the device output repeatability. The Hall element can be considered as a resistor array similar to a Wheatstone bridge. A large portion of the offset is a result of the mismatching of these resistors. The chopper-stabilizing technique cancels the mismatching of the resistors by changing the direction of the current flowing through the Hall plate and Hall voltage measurement taps, while maintaining the Hall-voltage signal that is induced by the external magnetic flux. The signal is, then, captured by a sample-and-hold circuit. More detailed descriptions of the circuit operation can be found in: Technical Paper STP 97-10, Monolithic Magnetic Hall Sensor Using Dynamic Quadrature Offset Cancellation and Technical Paper STP 99-1, ChopperStabilized Amplifiers With A Track-and-Hold Signal Demodulator.
+V
REG
X
B +V
--
HALL VOLTAGE
+
Dwg. AH-011-2
Operation. The output of these devices switches low (turns on) when a magnetic field perpendicular to the Hall sensor exceeds the operate point threshold (BOP). After turn-on, the output is capable of sinking 30 mA and the output voltage is VOUT(SAT). When the magnetic field is reduced below the release point (BRP), the device output switches high (turns off). Note especially that release can occur when the magnetic field is removed but to ensure release, a field reversal is required. The difference in the magnetic operate and release points is the hysteresis (Bhys) of the device. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise.
VCC
OUTPUT VOLTAGE
B RP
B OP
VOUT(SAT)
0 -B 0 FLUX DENSITY +B
Dwg. GH-034-5
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SAMPLE & HOLD
Dwg. EH-012
7
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
APPLICATIONS INFORMATION
+B
BOP1 BRP1
-B +B BOP2 BRP2 -B
OUTE1
OUTE2
Dwg. WH-012-1
Quadrature/Direction Detection. External logic circuitry can be used to determine the direction of movement of the magnetic field across the face of the package. For the direction signal to be appropriately updated, a quadrature relationship must be maintained between the ring magnet pole width*, the sensor-to-sensor spacing, and, to a lesser extent, the magnetic switch points. For optimal design, the sensor should be actuated with a ring magnet pole width* two times the sensor-to-sensor spacing. This will produce a sinusoidal magnetic field whose period (denoted as ) is then four times the sensorto-sensor spacing. A quadrature relationship can also be maintained for a ring magnet that has a period that satisfies the relationship n/4 = 1.0 mm, where n is any odd integer. Therefore, ring magnets with pole-pair spacings equal to 4 mm (n = 1), 1.3 mm (n = 3), etc. are permitted. The response of the device to the magnetic field produced by a rotating ring magnet is shown above. Note the desired phase shift between the two integrated sensors.
Over-Current Protection. Current through each output transistor is sensed with a low-value (<1 ) on-chip aluminum resistor. The voltage drop across this resistor is fed back to control the base drive of that output. This feedback prevents the output transistor from exceeding its maximum current-density rating by limiting the output current to between 30 mA and 55 mA. In this mode, the device will come out of saturation and dissipate an increased amount of power PD = VOUT x IOM where VOUT = VCC - (IOM x RL) and the output transistor will be thermally stressed. This stress, unless protected against, will cause the device junction temperature to rise until it fails catastrophically. Over-current limiting is intended to protect the device from transient overloads and should not imply that output short circuits are permitted.
* "Pole" refers to a single pole (North or South) unless stated as "pole pair" (North and South).
8
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
APPLICATIONS INFORMATION (cont'd)
Power Dissipation and Junction Temperature. Operating characteristics are limited by allowable package power dissipation (PD) as a function of ambient temperature (TA), which is defined by the maximum internal junction temperature (TJ = 170C) and the package thermal resistance (RJA = 177C/W). PD = (TJ - TA)/RJA = (170 - TA)/177 This is shown in the graph on page 2. Actual or required package power dissipation is the sum of the two output powers (d.c. x IOUT1 x VOUT(SAT)1) + (d.c. x IOUT2 x VOUT(SAT)2) and the sensor power (ICC x VCC). At high ambient operating temperatures (above about 120C), it is easy to exceed the allowable package power dissipation. In this case, the output currents or the supply voltage must be reduced. Operation with Fine-Pitch Ring Magnets. For targets with a circular pitch of less than 4 mm, a performance improvement can be observed by rotating the front face of the sensor subassembly (see below). This sensor rotation decreases the effective sensor-to-sensor spacing, provided that the Hall elements are not rotated beyond the width of the target. Applications. It is strongly recommended that an external 0.01 F bypass capacitor be connected (in close proximity to the Hall sensor) between the supply and ground of the device to reduce both external noise and noise generated by the internal logic. The simplest form of magnet that will operate these devices is a ring magnet. Other methods of operation, such as linear magnets, are possible. Extensive applications information on magnets and Hall-effect sensors is also available in the "Hall-Effect IC Applications Guide" which can be found in the latest issue of the Allegro MicroSystems Electronic Data Book, AMS-702 or Application Note 27701, or at
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0.039 COS (inch)
1.00 COS (mm)
0.039" 1.00 mm
TARGET FACE WIDTH, F >1.00 SIN (mm)
Rotated sensor for fine-pitch ring magnets
A
>0.039 SIN (inch)
1
A
1 2 3 4
2 3 4
Dwg. MH-024-1
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9
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
Dimensions in Inches
(controlling dimensions)
0.208 0.203
Dimensions in Millimeters
(for reference only)
5.28 5.16
45
0.063 0.059
45
1.60 1.50
0.138 0.133 45 0.085
MAX
3.51 3.38 45 2.16
MAX
1
2
3
4
0.033
1
2
3
4
0.84
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-009D in
0.48 0.36
1.27
BSC
Dwg. MH-009D mm
SURFACE-MOUNT LEAD FORM (order A3425LK-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. Tolerances on package height and width represent allowable mold offsets. Dimensions given are measured at the widest point (parting line). 2. Exact body and lead configuration at vendor's option within limits shown. 3. Height does not include mold gate flash. 4. Recommended minimum PWB hole diameter to clear transition area is 0.035" (0.89 mm). 5. Where no tolerance is specified, dimension is nominal.
10
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
This page is intentionally left blank.
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11
3425 DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE, BIPOLAR HALL-EFFECT SWITCH
HALL-EFFECT SENSORS
Partial Part Number 3060 3422 3059 3056 3058 3421 3054 3209 3210 3421 3422 3425 Avail. Oper. Characteristics at TA = +25C Temp. BOP max BRP min Bhys typ K/S E/L K/S E/L E/L E/L K/S E E E/L E/L L +35 +75 +100 +150 +250 +280 -35 -75 -100 -150 -250 -280 30 46 130 50 200 335 Features ac coupled direction detection ac coupled zero-speed zero-speed direction detection 6 Notes GEARTOOTH/RING MAGNET (DUAL ELEMENT) HALL-EFFECT SENSORS in order of BOP
SPECIAL-PURPOSE HALL-EFFECT SENSORS +300 +5.0 50 unipolar switch, multiplexed 60 5.0 7.7 400 W, chopper stabilized 60 5.0 7.7 25 W, chopper stabilized +280 -280 335 direction detection +85 -85 46 direction detection +24 -24 19 dual, chopper stabilized
1
Operating Temperature Ranges: S = -20C to +85C, E = -40C to +85C, J = -40C to +115C, K = -40C to +125C, L = -40C to +150C Notes 1. Protected. 6. Multiplexed two-wire sensor; after proper address, power/signal bus current indicates magnetic field condition.
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.
12
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

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