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 +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 me-
chanical location tolerance when manufactured discretely. The
A3425LK is an ultra-sensitive device optimized for use with high-
density ring magnets.
The device includes on a single silicon chip a voltage regulator, two
independent
chopper-stabilized Hall-voltage generators , two small-
signal 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.
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 T
A
= +25
°
C
Supply Voltage, V
CC
........................
26.5 V
Reverse Battery Voltage, V
RCC
..........
-18 V
Zener Current, I
Z
............................
100 mA
Magnetic Flux Density, B ...........
Unlimited
Output Off Voltage, V
OUT
....................
V
CC
Output Current, I
OUT
........................
30 mA
Reverse Output Current, I
OUT
........
-50 mA
Package Power Dissipation, P
D
.
See Graph
Junction Temperature, T
J
...............
+170
°
C
Operating Temperature Range,
T
A
, ............................
-40
°
C to +150
°
C
Storage Temperature Range,
T
S
..............................
-65
°
C to +170
°
C
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
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
V
CC
I
OFF
V
OUT(SAT)
I
OM
f
C
t
r
t
f
I
CC
R
L
= 820
Ω,
C
L
= 10 pF
R
L
= 820
Ω,
C
L
= 10 pF
Both outputs off, V
CC
≤
26.5 V
Both outputs on, V
CC
≤
26.5 V
Reverse Battery Current
Zener Voltage
Zener Impedance
I
CC
V
Z
+ V
D
z
z
+ z
D
V
RCC
= -18 V
I
CC
= 15 mA, T
A
= 25°C
I
CC
= 15 mA, T
A
= 25°C
Test Conditions
Operating, T
J
< 170°C
1
V
OUT
= 18 V, B < B
RP
I
OUT
= 20 mA, B > B
OP
B > B
OP
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
µA
mV
mA
kHz
ns
ns
mA
mA
mA
V
Ω
NOTES:1. Supply voltage is limited by allowable package power dissipation as a function of ambient temperature.
2. B
OP
= operate point (output turns on); B
RP
= release point (output turns off).
3. Typical Data is at T
A
= +25°C and V
CC
= 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
B
OP1
B
OP2
Release Point
B
RP1
B
RP2
Hysteresis
Operate Differential
Release Differential
Symmetry
B
hys
B
OP(dif)
B
RP(dif)
B
sym
B
OP
– B
RP
B
OP1
– B
OP2
B
RP1
– B
RP2
B
OP
+ B
RP
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 T
A
= +25°C and V
CC
= 12 V and is for design information only.
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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
B
OP
/B
RP
DIFFERENTIAL IN GAUSS
10
5
0
-5
-10
-15
-20
-25
-50
B
RP
V
CC
= 3.3 V
V
CC
= 5 V
V
CC
= 18 V
B
OP
V
CC
= 3.3 V
V
CC
= 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
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