A3425
Ultra-Sensitive Dual-Channel Quadrature Hall-Effect Bipolar Switch
The A3425 is a dual-output channel, bipolar switch with two separate Hall-effect
sensor circuits, each providing a separate digital output for speed and direction
signal processing capability. Each sensor circuit has its own independent Hall
element, which are photolithographically aligned to better than 1 µm. Maintaining
accurate mechanical location between the two active Hall elements eliminates the
major manufacturing hurdle encountered in
fi
ne-pitch detection applications. The
A3425 is a highly sensitive, temperature-stable magnetic sensing device, which
is ideal for use in ring magnet-based speed and direction systems used in harsh
automotive and industrial environments.
The A3425 monolithic integrated circuit contains two independent Hall effect
switches, located approximately 1 mm apart. The digital outputs are 90º out of
phase so that the outputs are in quadrature with the proper ring magnet design.
This allows for easy processing of speed and direction signals. Extremely low-
drift amplifiers guarantee symmetry between the switches to maintain signal
quadrature. The patented chopper stabilization technique cancels offsets in
each channel, and provides stable operation over the operating temperature and
voltage ranges. An on-chip regulator allows the use of this device over a wide
operating voltage range. Post-assembly factory programming provides sensitive
switchpoints that are symmetrical between the two switches.
The A3425 is available in a plastic 8-pin SOIC surface mount package and a plas-
tic 4-pin SIP, both in two temperature ranges. Each package is available in a lead
(Pb) free version with 100% matte tin plated leadframe.
Package L, 8-pin SOIC
VCC
OUTPUTA
OUTPUTB
GND
1
2
3
4
8
7
6
5
No connection
No connection
No connection
No connection
Package K, 4-pin SIP
1. VCC
2. OUTPUTA
3. OUTPUTB
4. GND
1
2
3
4
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
.......................................
26.5 V
Reverse-Battery Voltage, V
RCC
........................
–18 V
Output Off Voltage, V
OUTPUT
..............................V
CC
Output Sink Current, I
OUTPUT(SINK)
.
Internally Limited
Magnetic Flux Density, B ..........................
Unlimited
Operating Temperature
Ambient, T
A
, Range E..................
–40ºC to 85ºC
Range L................
–40ºC to 150ºC
Maximum Junction, T
J(max)
........................165ºC
Storage Temperature, T
S
..................
–65ºC to 170ºC
Features and Benefits
•
Two matched Hall effect switches on a single substrate
•
•
•
•
•
•
•
Sensor element spacing approximately 1 mm
Superior temperature stability
3.3 V to 18 V operation
Integrated ESD diode from OUTPUT and VCC pins to GND
High-sensitivity switchpoints
Robust structure for EMC protection
Solid-state reliability
A3425DS-Rev. !
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3425
Ultra-Sensitive Dual-Channel Quadrature Hall-Effect Bipolar Switch
Functional Block Diagram
VCC
Programmable
Trim
Regulator
8 Bits
4 Bits
Sample and Hold
Dynamic Offset
Cancellation
OUTPUTA
Low-
Pass
Filter
Output
Drive
Amp
4 Bits
Sample and Hold
Dynamic Offset
Cancellation
OUTPUTB
Low-
Pass
Filter
Output
Drive
Amp
GND
Terminal List
Symbol
VCC
OUTPUTA
OUTPUTB
GND
–
Description
Connects power supply to on-chip voltage regulator
Output from
fi
rst Schmitt circuit
Output from second Schmitt circuit
Ground
No connection
Package
K
1
2
3
4
–
L
1
2
3
4
5, 6, 7, 8
A3425DS-Rev. !
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
A3425
Ultra-Sensitive Dual-Channel Quadrature Hall-Effect Bipolar Switch
Product Selection Guide
Part Number
A3425EK
A3425EK-T
A3425EKTN
A3425EKTN-T
A3425EL
A3425EL-T
A3425ELTR
A3425ELTR-T
A3425LK
A3425LK-T
A3425LKTN
A3425LKTN-T
A3425LL
A3425LL-T
A3425LLTR
A3425LLTR-T
Pb-free
–
Yes
–
Yes
–
Yes
–
Yes
–
Yes
–
Yes
–
Yes
–
Yes
Packing*
Bulk, 98 pieces/bag
Bulk, 98 pieces/bag
13-in. reel, 4000 pieces/reel
13-in. reel, 4000 pieces/reel
Bulk, 500 pieces/bag
Bulk, 500 pieces/bag
13-in. reel, 3000 pieces/reel
13-in. reel, 3000 pieces/reel
Bulk, 98 pieces/bag
Bulk, 98 pieces/bag
13-in. reel, 4000 pieces/reel
13-in. reel, 4000 pieces/reel
Bulk, 500 pieces/bag
Bulk, 500 pieces/bag
13-in. reel, 3000 pieces/reel
13-in. reel, 3000 pieces/reel
8-pin SOIC surface mount
4-pin SIP through hole
–40ºC to 150ºC
8-pin SOIC surface mount
4-pin SIP through hole
–40ºC to 85ºC
Mounting
Ambient, T
A
*Contact Allegro for additional packing options.
A3425DS-Rev. !
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A3425
Ultra-Sensitive Dual-Channel Quadrature Hall-Effect Bipolar Switch
OPERATING CHARACTERISTICS
Valid over operating temperature ranges unless otherwise noted; typical data applies to
V
CC
= 12 V, and T
A
= 25ºC
Characteristic
ELECTRICAL CHARACTERISTICS
Supply Voltage
1
Output Leakage Current
Output Rise Time
Output Fall Time
Supply Current
Low Output Voltage
Output Sink Current
Output Sink Current, Continuous
2
Output Sink Current, Peak
3
Chopping Frequency
V
CC
I
OUTPUT(OFF)
t
r
t
f
I
CC(OFF)
I
CC(ON)
V
OUTPUT(ON)
I
OUTPUT(SINK)
I
OUTPUT(SINK)C
I
OUTPUT(SINK)P
f
C
T
J
< T
J(max)
,V
OUTPUT
= 12 V
t < 3 seconds
Operating; T
A
≤
150°C
Either output
C
LOAD
= 20 pF, R
LOAD
= 820
Ω
C
LOAD
= 20 pF, R
LOAD
= 820
Ω
B < B
RP(A)
,B < B
RP(B)
B > B
OP(A)
,B > B
OP(B)
Both outputs; I
OUTPUT(SINK)
= 20 mA; B > B
OP(A)
,
B > B
OP(B)
3.3
–
–
–
–
–
–
–
–
–
–
–
<1
110
55
3.5
4.0
160
–
–
–
340
18
10
–
–
6.0
6.0
500
20
70
220
–
V
µA
ns
ns
mA
mA
mV
mA
mA
mA
kHz
Symbol
Test Conditions
Min. Typ.
Max
Units
TRANSIENT PROTECTION CHARACTERISTICS
Supply Zener Voltage
Supply Zener Current
4
Reverse-Battery Current
V
Z
I
Z
I
RCC
I
CC
= 15 mA
V
S
= 28 V
V
RCC
= –18 V, T
J
< T
J(max)
28
–
–
33
–
2
37
9.0
15
V
mA
mA
Continued on the next page...
A3425DS-Rev. !
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
A3425
Ultra-Sensitive Dual-Channel Quadrature Hall-Effect Bipolar Switch
OPERATING CHARACTERISTICS (continued)
Valid over operating temperature ranges unless otherwise noted; typical
data applies to V
CC
= 12 V, and T
A
= 25ºC
Characteristic
Symbol
Test Conditions
Min. Typ.
Max
Units
MAGNETIC CHARACTERISTICS, K Package
5
Operate Point: B > B
OP
Release Point: B < B
RP
Hysteresis: B
OP(A)
– B
RP(A)
,
B
OP(B)
– B
RP(B)
Symmetry: Channel A, Channel B,
B
OP(A)
+ B
RP(A)
, B
OP(B)
+ B
RP(B)
Operate Symmetry: B
OP(A)
– B
OP(B)
Release Symmetry: B
RP(A)
– B
RP(B)
B
OP(A)
, B
OP(B)
B
RP(A)
, B
RP(B)
B
HYS(A)
, B
HYS(B)
SYM
A
, SYM
B
SYM
AB(OP)
SYM
AB(RP)
–
–35
5
–40
–30
–30
7
–7
16
–
–
–
35
–
40
40
30
30
G
G
G
G
G
G
MAGNETIC CHARACTERISTICS, L Package
5
Operate Point: B > B
OP
Release Point: B < B
RP
Hysteresis: B
OP(A)
– B
RP(A)
,
B
OP(B)
– B
RP(B)
Symmetry: Channel A, Channel B,
B
OP(A)
+ B
RP(A)
, B
OP(B)
+ B
RP(B)
Operate Symmetry: B
OP(A)
– B
OP(B)
Release Symmetry: B
RP(A)
– B
RP(B)
1
2
B
OP(A)
, B
OP(B)
B
RP(A)
, B
RP(B)
B
HYS(A)
, B
HYS(B)
SYM
A
, SYM
B
SYM
AB(OP)
SYM
AB(RP)
–
–30
5
–35
–25
–25
7
–7
14
–
–
–
30
–
35
35
25
25
G
G
G
G
G
G
When operating at maximum voltage, never exceed maximum junction temperature, T
J(max)
. Refer to power derating curve charts.
Device will survive the current level specified, but operation within magnetic specification cannot be guaranteed.
3
Short circuit of the output to VCC is protected for the time duration specified.
4
Maximum specification limit is equivalent to I
CC(max)
+ 3 mA.
5
Magnetic
fl
ux density, B, is indicated as a negative value for north-polarity magnetic
fi
elds, and as a positive value for south-polarity
magnetic
fi
elds. This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the
relative strength of the
fi
eld is indicated by the absolute value of B, and the sign indicates the polarity of the
fi
eld (for example, a –100
G
fi
eld and a 100 G
fi
eld have equivalent strength, but opposite polarity).
EMC
Contact Allegro MicroSystems for EMC performance.
A3425DS-Rev. !
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
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