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
m, as contrasted with 100 m 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 +150C. A
similar device, with on-chip logic processing specifically for direction
detection applications, in a 5-pin SIP, is the A3422LKA.
FEATURES
I
Two Matched Hall Switches On A Single Substrate
I 1 mm Sensor-to-Sensor Spacing
I Superior Temperature Stability
I Resistant to Physical Stress
I Output Short-Circuit Protection
I Operation From Unregulated Supply
I Reverse Battery Protection
I Solid-State Reliability
I Integrated ESD Protection on Outputs and Supply
Data Sheet
27651.20
PRELIMINARY INFORMATION
(subject to change without notice)
August 21, 2000
Pinning is shown viewed from branded side.
DUAL, CHOPPER-STABILIZED, ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
3425
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
Always order by complete part number, e.g., A3425LK .
Dwg. PH-017
1
SUPPLY
V
CC
4
GROUND
3
2
X
OUTPUT
2
OUTPUT
1
X
3425
DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
www.allegromicro.com
3
ELECTRICAL CHARACTERISTICS over operating temperature range, each switch tested
separately (unless otherwise specified).
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Supply Voltage Range
V
CC
Operating, T
J
< 170
C
1
3.3
26.5
V
Output Leakage Current
I
OFF
V
OUT
= 18 V, B < B
RP
<1.0
10
A
Output Saturation Voltage
V
OUT(SAT)
I
OUT
= 20 mA, B > B
OP
225
400
mV
Output Current Limit
I
OM
B > B
OP
30
55
mA
Chopping Frequency
f
C
340
kHz
Output Rise Time
t
r
R
L
= 820
, C
L
= 10 pF
110
ns
Output Fall Time
t
f
R
L
= 820
, C
L
= 10 pF
55
ns
Total Supply Current
I
CC
Both outputs off, V
CC
26.5 V
3.8
6.0
mA
Both outputs on, V
CC
26.5 V
7.5
10
mA
Reverse Battery Current
I
CC
V
RCC
= -18 V
2.0
15
mA
Zener Voltage
V
Z
+ V
D
I
CC
= 15 mA, T
A
= 25
C
28
33
37
V
Zener Impedance
z
z
+ z
D
I
CC
= 15 mA, T
A
= 25
C
50
100
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
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Operate Point
B
OP1
8.0
24
G
B
OP2
11
24
G
Release Point
B
RP1
-24
-11
G
B
RP2
-24
-8.0
G
Hysteresis
B
hys
B
OP
B
RP
5.0
19
35
G
Operate Differential
B
OP(dif)
B
OP1
B
OP2
-2.0
30
G
Release Differential
B
RP(dif)
B
RP1
B
RP2
-3.3
30
G
Symmetry
B
sym
B
OP
+ B
RP
30
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.
3425
DUAL, CHOPPER-STABILIZED,
ULTRA-SENSITIVE,
BIPOLAR HALL-EFFECT SWITCH
www.allegromicro.com
5
SENSOR LOCATIONS
(
0.005" [0.13 mm] die placement)
Although sensor location is accurate to three sigma for a
particular design, product improvements may result in small
changes to sensor location.
A
1
4
3
2
Dwg. MH-001-4
0.015"
0.38 mm
NOM
0.053"
1.34 mm
BRANDED
SURFACE
ACTIVE AREA DEPTH
0.083"
2.11 mm
0.039"
1.00 mm
E1
E2
Allegro
TYPICAL OPERATING CHARACTERISTICS (cont'd)
as a function of supply voltage
OPERATE AND RELEASE DIFFERENTIALS
0
50
100
AMBIENT TEMPERATURE IN
C
-50
Dwg. GH-026-9
B
OP
/B
RP
DIFFERENTIAL IN GAUSS
0
5
150
-25
25
75
125
10
15
20
25
-25
-20
-15
-10
-5
B
OP
V
CC
= 3.3 V
V
CC
= 5-18 V
B
RP
V
CC
= 3.3 V
V
CC
= 5 V
V
CC
= 18 V
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