ALLEGRO A3425

Data Sheet
27651.20
3425
X
X
DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
1
2
3
4
SUPPLY
OUTPUT1
OUTPUT2
GROUND
V CC
Dwg. PH-017
Pinning is shown viewed from branded side.
PRELIMINARY INFORMATION
(subject to change without notice)
August 21, 2000
ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
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 ............... +170°C
Operating Temperature Range,
TA, ............................ -40°C to +150°C
Storage Temperature Range,
TS .............................. -65°C to +170°C
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 +150°C.
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 µm, as contrasted with 100 µm 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 -40°C to +150°C. A
similar device, with on-chip logic processing specifically for direction
detection applications, in a 5-pin SIP, is the A3422LKA.
FEATURES
■ Two Matched Hall Switches On A Single Substrate
■
■
■
■
■
■
■
■
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
SUPPLY
TO ALL
SUBCIRCUITS
DYNAMIC
OFFSET CANCELLATION
REG.
X
OUTPUT1
SAMPLE
& HOLD
E1
LOW-PASS
FILTER
1
2
CONTROL
CURRENT
LIMIT
DYNAMIC
OFFSET CANCELLATION
<1Ω
OUTPUT2
LOW-PASS
FILTER
X
SAMPLE
& HOLD
E2
3
CONTROL
CURRENT
LIMIT
<1Ω
GROUND
4
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
Dwg. FH-020-7
1.0
0.8
0.6
0.4
FREE AIR, R θJA = 177°C/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 © 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
Symbol
Test Conditions
Min.
Typ.
Max.
Units
3.3
–
26.5
V
Supply Voltage Range
VCC
Operating, TJ < 170°C1
Output Leakage Current
IOFF
VOUT = 18 V, B < BRP
–
<1.0
10
µA
VOUT(SAT)
IOUT = 20 mA, B > BOP
–
225
400
mV
B > BOP
30
–
55
mA
–
340
–
kHz
Output Saturation Voltage
Output Current Limit
IOM
Chopping Frequency
fC
Output Rise Time
tr
RL = 820 Ω, CL = 10 pF
–
110
–
ns
Output Fall Time
tf
RL = 820 Ω, CL = 10 pF
–
55
–
ns
Both outputs off, VCC ≤ 26.5 V
–
3.8
6.0
mA
Both outputs on, VCC ≤ 26.5 V
–
7.5
10
mA
VRCC = -18 V
–
2.0
15
mA
Total Supply Current
Reverse Battery Current
ICC
ICC
Zener Voltage
VZ + VD
ICC = 15 mA, TA = 25°C
28
33
37
V
Zener Impedance
zz + z D
ICC = 15 mA, TA = 25°C
–
50
100
Ω
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 = +25°C 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
Symbol
Operate Point
Release Point
Hysteresis
Min.
Typ.
Max.
Units
BOP1
–
8.0
24
G
BOP2
–
11
24
G
BRP1
-24
-11
–
G
BRP2
-24
-8.0
–
G
5.0
19
35
G
Bhys
Test Conditions
BOP – BRP
Operate Differential
BOP(dif)
BOP1 – BOP2
–
-2.0
±30
G
Release Differential
BRP(dif)
BRP1 – BRP2
–
-3.3
±30
G
BOP + BRP
–
–
±30
G
Symmetry
Bsym
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 = +25°C and VCC = 12 V and is for design information only.
www.allegromicro.com
3
3425
DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
TYPICAL OPERATING CHARACTERISTICS
as a function of temperature
CHANNEL 1 SWITCH POINTS
CHANNEL 2 SWITCH POINTS
25
25
20
20
15
VCC = 18-26.5 V
VCC = 3.3-5 V
10
SWITCH POINT IN GAUSS
SWITCH POINT IN GAUSS
15
OPERATE POINT
5
0
VCC = 5 V
VCC = 3.3 V
VCC = 18 V
VCC = 26.5 V
-5
-10
RELEASE POINT
-15
10
OPERATE POINT
VCC = 26.5 V
VCC = 5 V
VCC = 18 V
VCC = 3.3 V
5
0
-5
-10
RELEASE POINT
-15
-20
-25
-50
VCC = 26.5 V
VCC = 18 V
VCC = 3.3-5 V
-20
-25
0
25
50
75
100
AMBIENT TEMPERATURE IN °C
125
150
-25
-50
-25
0
25
50
75
100
125
AMBIENT TEMPERATURE IN °C
Dwg. GH-026-7
OUTPUT SATURATION VOLTAGE
150
Dwg. GH-026-8
TOTAL SUPPLY CURRENT
300
B ≥ BOP
8
SUPPLY CURRENT IN mA
SATURATION VOLTAGE IN mV
200
100
IOUT = 20 mA
0
-50
-25
0
VCC = 18 V
VCC = 26.5 V
VCC = 3.3 V
25
50
75
100
125
VCC = 3.3 V
6
B ≤ BRP
4
VCC = 18 V
VCC = 3.3 V
2
150
AMBIENT TEMPERATURE IN °C
0
-50
-25
0
25
Dwg. GH-029-5
4
50
75
100
125
150
AMBIENT TEMPERATURE IN °C
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Dwg. GH-028-8
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
BOP/BRP DIFFERENTIAL IN GAUSS
15
10
5
BOP
VCC = 3.3 V
VCC = 5-18 V
0
-5
BRP
VCC = 3.3 V
VCC = 5 V
VCC = 18 V
-10
-15
-20
-25
-50
-25
0
25
50
75
100
125
AMBIENT TEMPERATURE IN °C
ACTIVE AREA DEPTH
0.015"
0.38 mm
NOM
150
Dwg. GH-026-9
0.039"
1.00 mm
0.083"
2.11 mm
0.053"
1.34 mm
E1
SENSOR LOCATIONS
A
(±0.005" [0.13 mm] die placement)
BRANDED
SURFACE
Allegro
E2
1
2
3
4
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.
6
Qualification Test
Test Method and Test Conditions
Test Length
Samples
Biased Humidity (HAST)
JESD22-A101,
TA = 85°C, RH = 85%
1000 hrs
77
High-Temperature
Operating Life (HTOL)
JESD22-A108,
TA = 150°C, TJ = 165°C
1000 hrs
77
Accelerated HTOL
TA = 170°C, TJ = 180°C
168 hrs
77
Autoclave, Unbiased
JESD22-A102, Condition C,
96 hrs
77
High-Temperature
(Bake) Storage Life
MIL-STD-883, Method 1008,
TA = 170°C
1000 hrs
77
Temperature Cycle
MIL-STD-883, Method 1010,
-55°C to +150°C
1000 cycles
77
ESD,
Human Body Model
CDF-AEC-Q100-002
Pre/Post
Reading
x per
test
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Comments
VCC = VOUT = 3.3 V
Test to failure,
All leads > TBD
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.
SAMPLE
& HOLD
REG
X
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.
Dwg. EH-012
B
+V
—
HALL
VOLTAGE
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.
+
Dwg. AH-011-2
+V
www.allegromicro.com
VCC
OUTPUT VOLTAGE
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.
B RP
B OP
VOUT(SAT)
0
-B
0
FLUX DENSITY
+B
Dwg. GH-034-5
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 Τ) 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 nΤ/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 Ω) 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 = 170°C) and the package
thermal resistance (RθJA = 177°C/W).
Applications. It is strongly recommended that an
external 0.01 µF 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
PD = (TJ – TA)/RθJA = (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
120°C), it is easy to exceed the allowable package power
dissipation. In this case, the output currents or the supply
voltage must be reduced.
1.00 COS α (mm)
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.
0.039 COS α (inch)
www.allegromicro.com
Rotated sensor for
fine-pitch ring
magnets
0.039"
1.00 mm
α
TARGET FACE WIDTH, F
>1.00 SIN α (mm)
A
>0.039 SIN α (inch)
1
2
A
3
1
2
3
4
4
Dwg. MH-024-1
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9
3425
DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
Dimensions in Inches
Dimensions in Millimeters
(controlling dimensions)
(for reference only)
5.28
5.16
0.208
0.203
0.063
0.059
45°
1.60
1.50
45°
3.51
3.38
0.138
0.133
45°
45°
0.085
1
2
3
0.033
4
2.16
1
2
3
0.84
4
MAX
MAX
0.0173
0.0138
0.600
0.560
0.44
0.35
15.24
14.23
SEE NOTE
SEE NOTE
0.0189
0.0142
0.48
0.36
0.050
BSC
1.27
BSC
Dwg. MH-009D mm
Dwg. MH-009D in
SURFACE-MOUNT LEAD FORM (order A3425LK-TL)
2.41
0.095
±0.13
±0.005
0.002
0.051
MAX
MAX
0.004 0°–8°
MAX
0.10
0.020
MIN
FLAT
MAX
Dwg. MH-015 in
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.
www.allegromicro.com
11
3425
DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
HALL-EFFECT SENSORS
Partial Part
Number
Avail. Oper.
Characteristics at TA = +25°C
Temp.
BOP max
BRP min
Bhys typ
Features
Notes
GEARTOOTH/RING MAGNET (DUAL ELEMENT) HALL-EFFECT SENSORS in order of BOP
3060
3422
3059
3056
3058
3421
3054
3209
3210
3421
3422
3425
K/S
E/L
K/S
E/L
E/L
E/L
+35
+75
+100
+150
+250
+280
-35
-75
-100
-150
-250
-280
30
46
130
50
200
335
ac coupled
direction detection
ac coupled
zero-speed
zero-speed
direction detection
K/S
E
E
E/L
E/L
L
SPECIAL-PURPOSE HALL-EFFECT SENSORS
+300
+5.0
50
unipolar switch, multiplexed
±60
±5.0
7.7
400 µW, chopper stabilized
±60
±5.0
7.7
25 µW, chopper stabilized
+280
-280
335
direction detection
+85
-85
46
direction detection
+24
-24
19
dual, chopper stabilized
6
1
Operating Temperature Ranges:
S = -20°C to +85°C, E = -40°C to +85°C, J = -40°C to +115°C, K = -40°C to +125°C, L = -40°C to +150°C
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