A1120, A1121, and A1125
Chopper Stabilized Precision Hall Effect Switches
Features and Benefits
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Unipolar switchpoints
Resistant to physical stress
Superior temperature stability
Output short-circuit protection
Operation from unregulated supply
Reverse battery protection
Solid-state reliability
Small package sizes
Description
The A1120, A1121, and A1125 Hall-effect, unipolar switches
are extremely temperature-stable and stress-resistant sensor
ICs, especially suited for operation 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.
Each device includes on a single silicon chip a voltage regulator,
Hall-voltage generator, small-signal amplifier, chopper
stabilization, Schmitt trigger, and a short-circuit protected
open-drain output to sink up to 25 mA.
An on-board regulator permits operation with supply voltages
of 3 to 24 V. The advantage of operating down to 3 V is that
the device can be used in 3 V applications or with additional
external resistance in series with the supply pin for greater
protection against high voltage transient events.
For the A1120 and A1121, a south pole of sufficient strength
turns the output on. Removal of the magnetic field turns the
output off. The A1125 is complementary, in that for these
devices, a south pole turns the A1125 output off, and removal
of the magnetic field turns the output on.
3-pin SIP (suffix UA)
Packages:
3-pin SOT23W (suffix LH)
Not to scale
Two package styles provide a magnetically optimized package
for most applications. Package type LH is a modified SOT23W,
surface mount package, while UA is a three-lead ultra-mini SIP
for through-hole mounting. Each package type is lead (Pb) free
(suffix, –T), with a 100% matte tin plated leadframe.
Functional Block Diagram
VCC
Regulator
To All Subcircuits
Amp
Sample and Hold
Dynamic Offset
Cancellation
Low-Pass
Filter
VOUT
Control
Current Limit
GND
A1120-DS, Rev. 11
A1120, A1121
and A1125
Chopper Stabilized Precision Hall Effect Switches
Selection Guide
Part Number
A1120ELHLX-T
A1120ELHLT-T
2
A1120EUA-T
A1120LLHLX-T
A1120LLHLT-T
2
A1120LUA-T
A1121ELHLX-T
A1121ELHLT-T
2
A1121EUA-T
A1121LLHLX-T
A1121LLHLT-T
2
A1121LUA-T
A1125ELHLX-T
A1125EUA-T
A1125LLHLX-T
A1125LUA-T
*
Contact Allegro
2
Available
Packing
1
13-in. reel, 10000 pieces/reel
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
13-in. reel, 10000 pieces/reel
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
13-in. reel, 10000 pieces/reel
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
13-in. reel, 10000 pieces/reel
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
13-in. reel, 10000 pieces/reel
Bulk, 500 pieces/bag
13-in. reel, 10000 pieces/reel
Bulk, 500 pieces/bag
Mounting
3-pin SOT23W surface mount
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SIP through hole
Ambient, T
A
Switchpoints
(Typ.)
B
OP
B
RP
Output In South (Positive)
Magnetic Field
–40ºC to 85ºC
35
–40ºC to 150ºC
On (logic low)
–40ºC to 85ºC
95
–40ºC to 150ºC
70
25
–40ºC to 85ºC
35
–40ºC to 150ºC
25
Off (logic high)
for additional packing options.
through authorized Allegro distributors only.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A1120, A1121
and A1125
Chopper Stabilized Precision Hall Effect Switches
Absolute Maximum Ratings
Characteristic
Forward Supply Voltage
Reverse Supply Voltage
Output Off Voltage
Continuous Output Current
Reverse Output Current
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
CC
V
RCC
V
OUT
I
OUT
I
ROUT
T
A
T
J
(max)
T
stg
Range E
Range L
Notes
Rating
26.5
–30
26
25
–50
–40 to 85
–40 to 150
165
–65 to 170
Units
V
V
V
mA
mA
ºC
ºC
ºC
ºC
Pin-out Diagrams
GND
3
Package LH
Package UA
1
VCC
2
VOUT
1
VCC
2
GND
3
VOUT
Terminal List
Name
VCC
VOUT
GND
Description
Connects power supply to chip
Output from circuit
Ground
Number
Package LH Package UA
1
1
2
3
3
2
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A1120, A1121
and A1125
Chopper Stabilized Precision Hall Effect Switches
ELECTRICAL CHARACTERISTICS
Valid valid over full operating voltage and ambient temperature ranges; unless otherwise noted
Characteristics
Electrical Characteristics
Forward Supply Voltage
Output Leakage Current
V
CC
I
OUTOFF
Operating, T
J
< 165°C
A1120,
A1121
A1125
Output Saturation Voltage
V
OUT(SAT)
A1120,
A1121
A1125
Output Current Limit
I
OM
t
PO
f
C
t
r
t
f
I
CC(ON)
Supply Current
I
CC(OFF)
Reverse Supply Current
Supply Zener Clamp Voltage
Zener Impedance
Magnetic Characteristics
Operate Point
B
OP
A1120,
A1125
A1121
Release Point
B
RP
A1120,
A1125
A1121
Hysteresis
1
Typical
2
1
Symbol
Test Conditions
Min.
3
–
–
–
–
30
30
–
–
Typ.
1
–
–
–
185
185
–
–
–
800
0.2
0.1
–
–
–
–
–
–
50
Max.
24
10
10
500
500
60
60
25
–
2
2
4
4
4
4
–5
–
–
Unit
2
V
μA
μA
mV
mV
mA
mA
μs
kHz
μs
μs
mA
mA
mA
mA
mA
V
Ω
V
OUT
= 24 V, B < B
RP
V
OUT
= 24 V, B > B
OP
I
OUT
= 20 mA, B > B
OP
I
OUT
= 20 mA, B < B
RP
B > B
OP
B < B
RP
A1120,
A1121
A1125
Power-On Time
3
Chopping Frequency
Output Rise Time
3,4
Output Fall Time
3,4
V
CC
> 3.0 V, B < B
RP
(min) – 10 G,
B > B
OP
(max) + 10 G
R
L
= 820
Ω,
C
S
= 20 pF
R
L
= 820
Ω,
C
S
= 20 pF
A1120,
A1121
A1125
A1120,
A1121
A1125
V
CC
= 12 V, B > B
OP
V
CC
= 12 V, B < B
RP
V
CC
= 12 V, B < B
RP
V
CC
= 12 V, B > B
OP
–
–
–
–
–
–
–
28
–
I
RCC
V
Z
I
Z
V
RCC
= –30 V
I
CC
= 5 mA; T
A
= 25°C
I
CC
= 5 mA; T
A
= 25°C
–
50
5
40
(B
OP
– B
RP
)
–
10
35
95
25
70
10
25
50
135
–
110
–
42
G
G
G
G
G
G
B
HYS
A1120,
A1125
A1121
data are are at T
A
= 25°C and V
CC
= 12 V, and are for initial design estimations only.
G (gauss) = 0.1 mT (millitesla).
3
Guaranteed by device design and characterization.
4
C = oscilloscope probe capacitance.
S
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A1120, A1121
and A1125
Chopper Stabilized Precision Hall Effect Switches
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions
Package LH, 1-layer PCB with copper limited to solder pads
Package Thermal Resistance
R
θJA
Package LH, 2-layer PCB with 0.463 in.
2
of copper area each
side connected by thermal vias
Package UA, 1-layer PCB with copper limited to solder pads
Value Units
228
110
165
ºC/W
ºC/W
ºC/W
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
20
40
Power Derating Curve
T
J(max)
= 165ºC; I
CC
= I
CC(max)
V
CC(max)
Maximum Allowable V
CC
(V)
Package LH, 2-layer PCB
(R
JA
= 110 ºC/W)
Package UA, 1-layer PCB
(R
JA
= 165 ºC/W)
Package LH, 1-layer PCB
(R
JA
= 228 ºC/W)
V
CC(min)
60
80
100
120
140
160
180
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
20
Power Dissipation, P
D
(mW)
Pa
(R cka
ge
JA
= 1 LH
10 , 2-
Pac
ºC lay
/W er
kag
(R
PC
)
eU
JA
=
A, 1
B
165
-lay
ºC/
er P
W)
CB
Pac
k
(R age LH
,1
JA
= 2
28 º -layer
PCB
C/W
)
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
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