3150
PROGRAMMABLE, CHOPPER-
STABILIZED, HALL-EFFECT SWITCH
The A3150JLT and A3150JUA programmable switches provide
tooth/valley recognition in large gear-tooth sensing applications. Each
sensor consists of a single element, chopper-stabilized Hall-effect IC
that can be programmed to the desired magnetic switch point, opti-
mizing sensor airgap and timing accuracy performance after final
packaging. The small package can be easily assembled and used in
conjunction with a wide variety of gear/target shapes and sizes. The
two devices differ only in package style.
The sensing technology used for this sensor is Hall-effect based.
The sensor incorporates a single-element Hall IC that switches in
response to magnetic signals created by a ferrous target. The program-
mability of the circuit eliminates magnet and system offsets such as
those caused by tilt yet provides zero-speed detection capabilities
without the associated running jitter inherent in classical digital solu-
tions.
A proprietary dynamic offset cancelation technique, with an
internal high-frequency clock, reduces the residual offset voltage,
which is normally caused by device overmolding, temperature
dependancies, and thermal stress. This technique produces devices that
have an extremely stable quiescent output voltage, are immune to
mechanical stress, and have precise recoverability after temperature
cycling. Many problems normally associated with low-level analog
signals are minimized by having the Hall element and amplifier in a
single chip. Output precision is obtained by internal gain adjustments
during the manufacturing process and operate-point programming in the
user’s application.
This sensor system is ideal for use in gathering speed, position, and
timing information using gear-tooth-based configurations. The
A3150JLT/JUA are particularly suited to those applications that require
accurate duty cycle control or accurate edge detection. The lower
vibration sensitivity also makes these devices extremely useful for
transmission speed sensing.
Continued next page
Data Sheet
27621.40
X
PTCT
PRELIMINARY INFORMATION
(subject to change without notice)
ABSOLUTE MAXIMUM RATINGS
at T
A
= 25
°
C
Supply Voltage, V
CC
...........................
26.5 V
Reverse Supply Voltage, V
RCC
............
-30 V
Overvoltage Supply Current, I
CC
.....
100 mA
Magnetic Flux Density, B ............
Unlimited
Output Current, I
OUT
.....
Internally Limited
Output OFF Voltage, V
OUT
.................
26.5 V
Reverse Output Current, I
ROUT
.........
-50 mA
Operating Temperature Range,
T
A
...............................
-40
°
C to +115
°
C
Storage Temperature, T
S
...................
+170
°
C
T
C .
U LY
D N
O O
n
R
P E sig
D NC de
E E
U R
w
IN E ne
T F r
N E fo
O R 0
C R 5
IS O 32
D F A
— se
U
V
CC
1
2
3
GROUND
Dwg. PH-003-2
April 12, 1999
OUTPUT
SUPPLY
Always order by complete part number: the prefix 'A' + the basic four-digit
part number + a suffix to indicate operating temperature range +
a suffix to indicate package style, e.g.,
A3150JLT .
3150
PROGRAMMABLE, CHOPPER-
STABILIZED, PRECISION,
HALL-EFFECT SWITCH
FUNCTIONAL BLOCK DIAGRAM
1
SUPPLY
REG.
PROGRAM
LOGIC
OFFSET
ADJUST
DYNAMIC
OFFSET CANCELLATION
POWER-UP
OUTPUT
SAMPLE
& HOLD
X
LOW-PASS
FILTER
3
CONTROL
CURRENT
LIMIT
<1Ω
GROUND
2
Dwg. FH-020-3
Two package styles provide a magnetically opti-
mized package for most applications. Suffix ‘–LT’ is a
miniature SOT-89/TO-243AA transistor package for
surface-mount applications; while suffix ‘–UA’ is a
three-lead ultra-mini-SIP for through-hole mounting.
FEATURES AND BENEFITS
s
Chopper Stabilized for
Extremely Low Switch-Point Drift and
Immunity to Mechanical Stress
s
Externally Programmed Switch Point
s
On-Chip Supply-Transient Protection
s
Output Short-Circuit Protection
s
Single-Chip Sensing IC for High Reliability
s
Small Mechanical Size
s
<50
µs
Power-On Time
s
Wide Operating Voltage Range
s
Defined Power-On State
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 2000, Allegro MicroSystems, Inc.
3150
PROGRAMMABLE, CHOPPER-
STABILIZED, PRECISION,
HALL-EFFECT SWITCH
ELECTRICAL CHARACTERISTICS over operating voltage and temperature range (unless
otherwise noted).
Limits
Characteristic
Supply Voltage
Power-On State
Low Output Voltage
Output Current Limit
Output Leakage Current
Supply Current
Symbol
V
CC
POS
V
OUT(SAT)
I
OUTM
I
OFF
I
CC
Test Conditions
Operating, T
J
< 165°C
After programming, V
CC
= 0
¡
5 V
I
OUT
= 20 mA
V
OUT
= 12 V
V
OUT
= 24 V
Before programming, output OFF
Before programming, output ON
Reverse Supply Current
Power-On Delay
Output Rise Time
Output Fall Time
Clock Frequency
Zener Voltage
Zener Impedance
I
RCC
t
on
t
r
t
f
f
C
V
Z
z
z
I
ZT
= 100
µA,
T
A
= 25°C
I
ZT
= 10 mA, T
A
= 25°C
V
RCC
= -30 V
V
CC
> 5 V
R
L
= 820
Ω,
C
L
= 20 pF
R
L
= 820
Ω,
C
L
= 20 pF
Min.
4.25
HIGH
–
65
–
–
–
–
–
–
–
–
27
–
Typ.
–
HIGH
175
80
0.2
4.0
5.0
–
20
200
100
340
32
50
Max.
26
HIGH
400
95
10
7.0
8.0
-5.0
50
–
–
–
–
100
Units
V
–
mV
mA
µA
mA
mA
mA
µs
ns
ns
kHz
V
Ω
NOTE: Typical data is at V
CC
= 5 V and T
A
= +25°C and is for design information only.
MAGNETIC CHARACTERISTICS over operating supply voltage and temperature ranges.
Limits
Characteristic
Operate Point
Symbol
B
OP
Test Conditions
Programmable offset range
Initial (before programming)
Resolution
∆B
OP
Hysteresis
B
hys
V
CC
= 14 V, after programming, B
OP
≈
500 G
Min.
500
0
8.0
-35
5.0
Typ.
670
20
11
8.0
20
Max.
850
40
14
+35
35
Units
G
G
G
G
G
NOTE: Typical data is at V
CC
= 5 V and T
A
= +25°C and is for design information only.
www.allegromicro.com
3150
PROGRAMMABLE, CHOPPER-
STABILIZED, PRECISION,
HALL-EFFECT SWITCH
TYPICAL ELECTRICAL CHARACTERISTICS
5.0
10
T
A
= +25°C
4.0
SUPPLY CURRENT IN mA
SUPPLY CURRENT IN mA
B > B
OP
V
CC
= 5 V
8.0
6.0
B > B
OP
4.0
B < B
RP
2.0
3.0
B < B
RP
2.0
1.0
-50
-25
0
25
50
75
100
125
150
0
0
5
10
15
20
25
AMBIENT TEMPERATURE IN
°C
Dwg. GH-053-2
SUPPLY VOLTAGE IN VOLTS
Dwg. GH-041-2
300
I
OUT
= 20 mA
V
CC
= 4.5–24 V
SATURATION VOLTAGE IN mV
200
100
0
-50
-25
0
25
50
75
100
125
150
AMBIENT TEMPERATURE IN
°C
Dwg. GH-040-4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
3150
PROGRAMMABLE, CHOPPER-
STABILIZED, PRECISION,
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 repeatabil-
ity.
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.
Operation.
The output of these devices switches low (turns
ON) when a magnetic field (south pole) perpendicular to the
Hall sensor exceeds the operate point threshold (B
OP
). After
turn-ON, the output is capable of sinking 25 mA and the output
voltage is V
OUT(SAT)
. When the magnetic field is reduced below
the release point (B
RP
), the device output goes high (turns OFF).
The difference in the magnetic operate and release points is the
hysteresis (B
hys
) of the device. This built-in hysteresis allows
clean switching of the output even in the presence of external
mechanical vibration and electrical noise.
Applications.
It is strongly recommended that an external
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 chopper-stabiliza-
tion technique.
The simplest form of magnet that will operate these devices
is a bar magnet with the south-seeking pole towards the branded
surface of the device. Many other methods of operation are
possible. Extensive applications information on magnets and
Hall-effect sensors is also available in the
Allegro Electronic
Data Book
AMS-702 or
Application Note
27701, or
REG
X
B
+V
—
HALL
VOLTAGE
+
Dwg. AH-011-2
+V
V
CC
OUTPUT VOLTAGE
B
RP
B
OP
V
OUT(SAT)
0
0
FLUX DENSITY
+B
Dwg. GH-007-2
SUPPLY
3
PTCT
2
0.1
µF
CC
1
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V
Dwg. EH-013
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SAMPLE
& HOLD
Dwg. EH-012
OUTPUT
X
SUPPLY
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