A3245
Chopper-Stabilized Omnipolar Hall-Effect Switches
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: October 31, 2011
Recommended Substitutions:
For existing customer transition, and for new customers or new appli-
cations, refer to the
A1126.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
A3245
Chopper-Stabilized Omnipolar Hall-Effect Switches
Features and Benefits
▪
Omnipolar operation
▪
Chopper stabilization
▫
Superior temperature stability
▫
Extremely low switchpoint drift
▫
Insensitive to physical stress
▪
Reverse battery protection
▪
Output short circuit protection
▪
Solid state reliability
▪
Small size
▪
Robust EMC capability
▪
High ESD ratings (HBM)
Description
The A3245 integrated circuit is an omnipolar, ultrasensitive
Hall-effect switch with a digital output. This device has an
integrated regulator permitting operation to 24 V, making
it the first omnipolar switch available for operation to 24 V.
This device is especially suited for operation over extended
temperature ranges, up to +150°C. Superior high-temperature
performance is made possible through an Allegro
®
patented
dynamic offset cancellation, which reduces the residual offset
voltage normally caused by device overmolding, temperature
excursions, and thermal stress.
The A3245 Hall-effect switch includes the following on a
single silicon chip: voltage regulator, Hall-voltage generator,
small-signal amplifier, chopper stabilization, Schmitt trigger,
and a short circuit protected open-drain output. Advanced
BiCMOS wafer fabrication processing is used to take advantage
of low-voltage requirements, component matching, very low
input-offset errors, and small component geometries.
The omnipolar operation of the A3245 allows activation with
either a north
or
a south polarity field of sufficient strength.
In the absence of a magnetic field, the output is off. This
Packages: 3 pin SOT23W (suffix LH)
Continued on the next page…
Not to scale
Functional Block Diagram
VCC
Regulator
To All Subcircuits
Sample and Hold
Dynamic Offset
Cancellation
Low-Pass
Filter
VOUT
Amp
Amp
Control
Current Limit
<1Ω
GND
A3245-DS, Rev. 12
A3245
Chopper-Stabilized Omnipolar Hall Effect Switches
Description (continued)
patented magnetic-polarity-independence feature makes this device
an excellent replacement for reed switches, with improved ease of
manufacturing, because the A3245 does not require manufacturers
to orient their magnets. These devices allow simple on/off switching
in industrial, consumer, and automotive applications.
The A3245 is rated for operation between the ambient temperatures
–40°C and 85°C for the E temperature range, and –40°C to 150°C
for the L temperature range. The small geometries of the BiCMOS
process allow these devices to be provided in ultrasmall packages.
Package LH is an SOT23W, a miniature low-profile surface-
mount package. It is lead (Pb) free, with 100% matte tin plated
leadframe.
Selection Guide
Part Number
A3245ELHLT-T
A3245LLHLT-T
Packing*
7-in. reel, 3000 pieces/reel
7-in. reel, 3000 pieces/reel
Mounting
3-pin SOT23W surface mount
3-pin SOT23W surface mount
Ambient, T
A
(°C)
–40 to 85
–40 to 150
*Contact Allegro for additional packing options.
Absolute Maximum Ratings
Characteristic
Supply Voltage
Reverse-Supply Voltage
Reverse-Supply Current
Output Off Voltage
Output Current
Magnetic Flux Density
Operating Ambient Temperature
Maximum Junction Temperature
Storage Temperature
Symbol
V
CC
V
RCC
I
RCC
V
OUT
I
OUTSINK
B
T
A
T
J
(max)
T
stg
Range E
Range L
Notes
Rating
28
–18
–2
28
Internally Limited
Unlimited
–40 to 85
–40 to 150
165
–65 to 170
Units
V
V
mA
V
–
G
ºC
ºC
ºC
ºC
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
A3245
Chopper-Stabilized Omnipolar Hall Effect Switches
OPERATING CHARACTERISTICS
valid over full operating voltage and ambient temperature ranges, unless otherwise noted
Characteristic
Electrical Characteristics
Supply Voltage
1
Output Leakage Current
Output On Voltage
Output Current Limit
Power-On Time
Chopping Frequency
Output Rise Time
2
Output Fall Time
2
Supply Current
Reverse Battery Current
Supply Zener Clamp Voltage
Supply Zener Current
3
Magnetic Characteristics
4
Operate Point
Release Point
Hysteresis
1
2
Symbol
V
CC
I
OUTOFF
V
OUT(SAT)
I
OM
t
PO
f
c
t
r
t
f
I
CCON
I
CCOFF
I
RCC
V
ZSupply
I
ZSupply
B
OPS
B
OPN
B
RPS
B
RPN
B
HYS
Test Conditions
Operating, T
J
< 165°C
V
OUT
= 24 V, B < B
RP
I
OUT
= 20 mA, B > B
OP
B > B
OP
V
CC
> V
CC(MIN)
R
LOAD
= 820
Ω,
C
S
= 20 pF
R
LOAD
= 820
Ω,
C
S
= 20 pF
B > B
OP
B < B
RP
V
RCC
= –18 V
I
CC
= 6.5 mA; T
A
= 25°C
V
S
= 28 V
South pole adjacent to branded face of device
North pole adjacent to branded face of device
South pole adjacent to branded face of device
North pole adjacent to branded face of device
|B
OPX
– B
RPX
|
Min.
3.6
–
–
30
–
–
–
–
–
–
–
28
–
15
–55
5
–50
5
Typ.
–
–
–
–
–
200
–
–
1.5
1.5
–
–
–
38
–38
20
–20
18
Max.
24
10
500
60
50
–
1
1
3.5
3.5
–2
–
6.5
55
–15
50
–5
30
Units
V
μA
mV
mA
μs
kHz
μs
μs
mA
mA
mA
V
mA
G
G
G
G
G
Maximum voltage must be adjusted for power dissipation and junction temperature, see
Power Derating
section.
C
S
= oscilloscope probe capacitance.
3
Maximum current limit is equal to the maximum I
CC(MAX)
+ 3 mA.
4
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).
DEVICE QUALIFICATION PROGRAM
Contact Allegro for information.
EMC (Electromagnetic Compatibility) REQUIREMENTS
Contact Allegro for information.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
A3245
Chopper-Stabilized Omnipolar Hall Effect Switches
Electrical Characteristic Data
Supply Current (On) versus Ambient Temperature
5.0
4.0
5.0
4.0
Supply Current (On) versus Supply Voltage
I
CCON
(mA)
3.0
2.0
1.0
0
–50
0
50
T
A
(°C)
100
150
I
CCON
(mA)
V
CC
(V)
24
3.6
T
A
(°C)
–40
25
150
3.0
2.0
1.0
0
0
5
10
V
CC
(V)
15
20
25
Supply Current (Off) versus Ambient Temperature
Supply Current (Off) versus Supply Voltage
5.0
4.0
5.0
4.0
I
CCOFF
(mA)
I
CCOFF
(mA)
V
CC
(V)
3.0
2.0
1.0
0
–50
0
50
T
A
(°C)
100
150
24
3.6
T
A
(°C)
–40
25
150
3.0
2.0
1.0
0
0
5
10
V
CC
(V)
15
20
25
Output Voltage (On) versus Ambient Temperature
500
450
400
350
500
450
400
350
Output Voltage (On) versus Supply Voltage
V
OUT(SAT)
(mV)
V
OUT(SAT)
(mV)
300
250
200
150
100
50
0
–50
0
50
T
A
(°C)
100
150
V
CC
(V)
24
3.6
300
250
200
150
100
50
0
0
5
10
V
CC
(V)
15
20
25
T
A
(°C)
–40
25
150
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
4
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