A3230
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
AB SO LUTE MAX I MUM RAT INGS
Supply Voltage, V
CC
..........................................28 V
Reverse-Supply Voltage, V
RCC
........................18 V
Output Off Voltage, V
OUT
............................... 26.5 V
Output Current, I
OUTSINK
........... Internally Limited
Reverse-Output Current, I
ROUT
....................10 mA
Magnetic Flux Density, B .........................Unlimited
Operating Temperature
Ambient,
T
A
, Range E.................. 40C to 85C
Ambient,
T
A
, Range L................ 40C to 150C
Maximum
Junction,
T
J(MAX)
......................165C
Storage Temperature, T
S
.................. 65C to 170C
Chopper-Stabilized
Hall-Effect Bipolar Switch
Package LH, 3-pin Surface Mount
Features and Benefi ts
Package UA, 3-pin SIP
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)
The A3230 Hall-effect sensor is a temperature stable, stress-resistant bipolar
switch. This sensor is the most sensitive Hall-effect device in the Allegro
bipolar
switch family and is intended for ring-magnet sensing. Superior high-temperature
performance is made possible through an Allegro patented dynamic offset cancel-
lation that utilizes chopper-stabilization. This method reduces the offset voltage
normally caused by device overmolding, temperature dependencies, and thermal
stress.
The A3230 includes the following on a single silicon chip: a voltage regulator,
Hall-voltage generator, small-signal amplifi er, chopper stabilization, Schmitt
trigger, and a short circuit protected open-drain output. Advanced BiCMOS wafer
fabrication processing takes advantage of low-voltage requirements, component
matching, very low input-offset errors, and small component geometries.
The A3230 Hall-effect bipolar switch turns on in a south polarity magnetic fi eld of
suffi cient strength and switches off in a north polarity magnetic fi eld of suffi cient
strength. Because the output state is not defi ned if the magnetic fi eld is diminished
or removed, to ensure that the device switches, Allegro recommends using mag-
nets of both polarities and of suffi cient strength in the application.
The A3230 is rated for operation between the ambient temperatures 40C and
85C for the E temperature range, and 40C to 150C for the L temperature
range.
Two A3230 package styles provide magnetically optimized solutions
for most applications. Package LH is a SOT23W, a miniature low-profi le
surface-mount package, while package UA is a three-lead ultramini SIP for
through-hole mounting. Each package is available in a lead (Pb) free version,
with 100% matte tin plated leadframes.
1
3
2
VCC
GND
VOUT
1
2
3
VCC
VOUT
GND
1
2
3
1 2
3
2
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
Product Selection Guide
Functional Block Diagram
Regulator
GND
VCC
VOUT
Control
Current Limit
<1
Dyna
mic O
ffse
t
Ca
nce
ll
a
t
i
o
n
Sam
p
le
and
H
o
ld
To All Subcircuits
Amp
Low-Pass
Filter
Terminal List
Name
Description
Number
Package LH
Package UA
VCC
Connects power supply to chip
1
1
VOUT
Output from circuit
2
3
GND
Ground
3
2
Part Number
Pb-
free
Packing*
Mounting
Ambient, T
A
(C)
B
RP(MIN)
(G)
B
OP(MAX)
(G)
A3230ELHLT
7-in. reel, 3000 pieces/reel
3-pin SOT23W surface mount
40 to 85
25
25
A3230ELHLT-T
Yes
A3230EUA
Bulk, 500 pieces/bag
3-pin SIP through hole
A3230EUA-T
Yes
A3230LLHLT
7-in. reel, 3000 pieces/reel
3-pin SOT23W surface mount
40 to 150
A3230LLHLT-T
Yes
A3230LUA
Bulk, 500 pieces/bag
3-pin SIP through hole
A3230LUA-T
Yes
*Contact Allegro for additional packing options.
3
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
OPERATING CHARACTERISTICS valid over full operating voltage and ambient temperature ranges, unless otherwise noted
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Electrical Characteristics
Supply Voltage
1
V
CC
Operating, T
J
< 165C
3.6
24
V
Output Leakage Current
I
OUTOFF
V
OUT
= 24 V, B < B
RP
10
A
Output On Voltage
V
OUT(SAT)
I
OUT
= 20 mA, B > B
OP
250
500
mV
Output Current Limit
I
OM
B > B
OP
30
60
mA
Power-On Time
t
PO
V
CC
> 3.6 V
8
50
s
Chopping Frequency
f
c
200
kHz
Output Rise Time
2
t
r
R
LOAD
= 820 , C
S
= 20 pF
0.2
1
s
Output Fall Time
2
t
f
R
LOAD
= 820 , C
S
= 20 pF
0.2
1
s
Supply Current
I
CCON
B > B
OP
1.6
5
mA
I
CCOFF
B < B
RP
1.6
5
mA
Reverse Battery Current
I
RCC
V
RCC
= 18 V
2
mA
Supply Zener Clamp Voltage
V
Z
I
CC
= 8 mA; T
A
= 25C
28
V
Supply Zener Current
3
I
Z
V
S
= 28 V
8
mA
Magnetic Characteristics
4
Operate Point
B
OP
South pole adjacent to branded face of device
10
7.5
25
G
Release Point
B
RP
North pole adjacent to branded face of device
25
7.5
10
G
Hysteresis
B
HYS
B
OP
B
RP
5
15
25
G
1
Maximum voltage must be adjusted for power dissipation and junction temperature, see Power Derating section.
2
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.
4
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
Electrical Characteristic Data
T
A
(C)
Supply Current (On) versus Ambient Temperature
V
CC
(V)
I
CCON
(mA)
24
3.6
T
A
(C)
Supply Current (Off) versus Ambient Temperature
V
CC
(V)
I
CCOFF
(mA)
24
3.6
T
A
(C)
Output Voltage (On) versus Ambient Temperature
V
CC
(V)
V
OUT(SA
T)
(mV)
24
3.6
Supply Current (On) versus Supply Voltage
T
A
(C)
I
CCON
(mA)
V
CC
(V)
40
25
150
Supply Current (Off) versus Supply Voltage
T
A
(C)
I
CCOFF
(mA)
V
CC
(V)
40
25
150
Output Voltage (On) versus Supply Voltage
T
A
(C)
V
OUT(SA
T)
(mV)
V
CC
(V)
40
25
150
0
1.0
2.0
3.0
4.0
5.0
0
1.0
2.0
3.0
4.0
5.0
0
1.0
2.0
3.0
4.0
5.0
0
1.0
2.0
3.0
4.0
5.0
50
0
50
100
150
0
5
10
15
20
25
50
0
50
100
150
0
5
10
15
20
25
50
0
50
100
150
0
5
10
15
20
25
0
50
200
250
100
150
300
350
400
450
500
0
50
200
250
100
150
300
350
400
450
500
5
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
V
CC
(V)
24
3.8
T
A
(C)
V
CC
(V)
24
3.8
V
CC
(V)
24
3.8
T
A
(C)
40
25
150
T
A
(C)
40
25
150
T
A
(C)
40
25
150
Operate Point versus Ambient Temperature
B
OP
(G)
T
A
(C)
Release Point versus Ambient Temperature
B
RP
(G)
T
A
(C)
Hysteresis versus Ambient Temperature
B
HYS
(G)
B
OP
(G)
B
RP
(G)
B
HYS
(G)
Operate Point versus Supply Voltage
Release Point versus Supply Voltage
V
CC
(V)
V
CC
(V)
T
A
(C)
V
CC
(V)
Hysteresis versus Supply Voltage
50
0
50
100
150
0
5
10
15
20
25
50
0
50
100
150
0
5
10
15
20
25
50
0
50
100
150
0
5
10
15
20
25
-10
-5
0
5
15
10
20
25
-10
-5
0
5
15
10
20
25
-25
-20
-15
0
5
-5
-10
10
-25
-20
-15
0
5
-5
-10
10
5
10
15
20
25
5
10
15
20
25
Magnetic Characteristic Data
6
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions
Value
Units
Package Thermal Resistance
R
JA
Package LH, minimum-K PCB (single-sided with
copper limited to solder pads)
110
C/W
Package LH, low-K PCB (double-sided with
0.926 in
2
copper area)
228
C/W
Package UA, minimum-K PCB (single-sided with
copper limited to solder pads)
165
C/W
Power Derating Curve
T
J(max)
= 165C; I
CC
= I
CC(max)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
20
40
60
80
100
120
140
160
180
Temperature (C)
M
a
x
i
mu
m A
l
l
o
w
a
b
l
e
V
CC
(V
)
Low-K PCB, Package LH
(R
JA
= 110 C/W)
Minimum-K PCB, Package UA
(R
JA
= 165 C/W)
Minimum-K PCB, Package LH
V
CC(max)
V
CC(min)
(R
JA
= 228 C/W)
Power Dissipation versus Ambient Temperature
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
20
40
60
80
100
120
140
160
180
Temperature (C)
P
o
w
e
r
D
i
s
s
ipa
t
ion, P
D
(m
W
)
Low-K PCB, Package LH
(R
JA
= 110 C/W)
Min-K PCB, Package LH
(R
JA
= 228 C/W)
Min-K PCB, Package UA
(R
JA
= 165 C/W)
7
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
Functional Description
B
OP
B
RP
B
HYS
V
OUT
V
OUT(SAT)
Switch to Low
Switch to High
V+
0
B
OP(MAX)
B
RP
B
HYS
V
OUT
V
OUT(SAT)
Switch to Low
Switch to High
V+
0
B
OP
B
RP(MIN)
B
HYS
V
OUT
V
OUT(SAT)
Switch to Low
Switch to High
V+
0
V
CC
V
CC
V
CC
B+
B
B+
B 0
0
B+
B
0
VCC
V
S
Sensor Output
GND
VOUT
R
LOAD
A3230
0.1 F
C
BYP
Operation
The output of these devices switches low (turns on) when a
magnetic fi eld perpendicular to the Hall sensor exceeds the
operate point threshold, B
OP
. After turn-on, the output voltage
is V
OUT(SAT)
. The output transistor is capable of sinking current
up to the short circuit current limit, I
OM
, which is a minimum of
30 mA. When the magnetic fi eld is reduced below the release
point, B
RP
, the device output goes high (turns off). The differ-
ence in the magnetic operate and release points is the hysteresis,
B
HYS
, of the device. This built-in hysteresis allows clean switch-
ing of the output even in the presence of external mechanical
vibration and electrical noise.
There are three switching modes for bipolar devices, referred to
as latch, unipolar switch, and negative switch. Mode is deter-
mined by the switchpoint characteristics of the individual device.
Note that, as shown in fi gure 1, these switchpoints can lie in
either north or south polarity ranges. The values of the magnetic
parameters for the A3230 are specifi ed in the Magnetic Charac-
teristics table, on page 3.
Bipolar devices typically behave as latches (although these
devices are not guaranteed to do so). In this mode, magnetic
fi elds of opposite polarity and equivalent strengths are needed
to switch the output. When the magnetic fi elds are removed
(B
0) the device remains in the same state until a magnetic
Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as that shown in panel D. Panel A
displays the hysteresis when a device exhibits latch mode (note that the B
HYS
band incorporates B= 0), panel B shows unipolar switch behavior (the
B
HYS
band is more positive than B = 0), and panel C shows negative switch behavior (the B
HYS
band is more negative than B = 0). Bipolar devices,
such as the A3230, can operate in any of the three modes.
(A)
(B)
(C)
(D)
fi eld of the opposite polarity and of suffi cient strength causes
it to switch. The hysteresis of latch mode behavior is shown in
panel A of fi gure 1.
In contrast to latching, when a device exhibits unipolar switch-
ing, it only responds to a south magnetic fi eld. The fi eld must
be of suffi cient strength, > B
OP
, for the device to operate. When
the fi eld is reduced beyond the B
RP
level, the device switches
back to the high state, as shown in panel B of fi gure 1. Devices
8
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
exhibiting negative switch behavior operate in a similar but
opposite manner. A north polarity fi eld of suffi cient strength,
> B
RP
, (more north than B
RP
) is required for operation, although
the result is that V
OUT
switches high, as shown in panel C. When
the fi eld is reduced beyond the B
OP
level, the device switches
back to the low state.
The A3230 is designed to attain a small hysteresis, and thereby
provide more sensitive switching. Although this means that
true latching behavior cannot be guaranteed in all cases, proper
switching can be ensured by use of both south and north mag-
netic fi elds, as in a ring magnet.
Bipolar devices adopt an indeterminate output state when
powered-on in the absence of a magnetic fi eld or in a fi eld that
lies within the hysteresis band of the device. The correct state is
attained after the fi rst excursion beyond B
OP
or B
RP
.
For more information on Bipolar switches, refer to Application
Note 27705, Understanding Bipolar Hall Effect Sensors.
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 stabilization technique. As is
shown in Panel B of fi gure 1, a 0.1F capacitor is typical.
Extensive applications information on magnets and Hall-effect
sensors is available in:
Hall-Effect IC Applications Guide, AN27701,
Hall-Effect Devices: Gluing, Potting, Encapsulating, Lead
Welding and Lead Forming, AN27703.1
Soldering Methods for Allegro's Products SMT and Through-
Hole, AN26009
All are provided in Allegro Electronic Data Book, AMS-702 and
the Allegro Web site: www.allegromicro.com
9
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
Figure 2. Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation)
Amp
Regulator
Clock/Logic
Hall Element
Sa
mp
le
an
d
Ho
ld
Lo
w-P
a
s
s
Filte
r
Chopper Stabilization Technique
When using Hall-effect technology, a limiting factor for
switchpoint accuracy is the small signal voltage developed
across the Hall element. This voltage is disproportionally small
relative to the offset that can be produced at the output of the
Hall sensor. This makes it diffi cult to process the signal while
maintaining an accurate, reliable output over the specifi ed oper-
ating temperature and voltage ranges.
Chopper stabilization is a unique approach used to minimize
Hall offset on the chip. The patented Allegro technique, namely
Dynamic Quadrature Offset Cancellation, removes key sources
of the output drift induced by thermal and mechanical stresses.
This offset reduction technique is based on a signal modulation-
demodulation process. The undesired offset signal is separated
from the magnetic-fi eld-induced signal in the frequency domain,
through modulation. The subsequent demodulation acts as a
modulation process for the offset, causing the magnetic-fi eld-
induced signal to recover its original spectrum at baseband,
while the dc offset becomes a high-frequency signal. The mag-
netic-fi eld-induced signal then can pass through a low-pass fi lter,
while the modulated dc offset is suppressed. This confi guration
is illustrated in fi gure 2.
The chopper stabilization technique uses a 200 kHz high-fre-
quency clock. For demodulation process, a sample and hold
technique is used, where the sampling is performed at twice the
chopper frequency (400 kHz). This high-frequency operation
allows a greater sampling rate, which results in higher accuracy
and faster signal-processing capability. This approach desensi-
tizes the chip to the effects of thermal and mechanical stresses,
and produces devices that have extremely stable quiescent Hall
output voltages and precise recoverability after temperature
cycling. This technique is made possible through the use of a
BiCMOS process, which allows the use of low-offset, low-noise
amplifi ers in combination with high-density logic integration and
sample-and-hold circuits.
The repeatability of magnetic-fi eld-induced switching is affected
slightly by a chopper technique. However, the Allegro high-
frequency chopping approach minimizes the affect of jitter and
makes it imperceptible in most applications. Applications that
are more likely to be sensitive to such degradation are those
requiring precise sensing of alternating magnetic fi elds; for
example, speed sensing of ring-magnet targets. For such applica-
tions, Allegro recommends its digital sensor families with lower
sensitivity to jitter. For more information on those devices,
contact your Allegro sales representative.
10
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
The device must be operated below the maximum junction
temperature of the device, T
J(max)
. Under certain combinations of
peak conditions, reliable operation may require derating sup-
plied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating T
J
. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, R
JA
, is a fi gure of merit sum-
marizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, R
JC
, is
relatively small component of R
JA
. Ambient air temperature,
T
A
, and air motion are signifi cant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, P
D
), can
be estimated. The following formulas represent the fundamental
relationships used to estimate T
J
, at P
D
.
P
D
= V
IN
I
IN
(1)
T = P
D
R
JA
(2)
T
J
= T
A
+ T
(3)
For example, given common conditions such as: T
A
= 25C,
V
CC
= 12 V, I
CC
= 1.5 mA, and R
JA
= 165 C/W, then:
P
D
= V
CC
I
CC
= 12 V
1.5 mA = 18 mW
T = P
D
R
JA
= 18 mW
165 C/W = 3C
T
J
= T
A
+
T = 25C + 3C = 28C
A worst-case estimate, P
D(max)
, represents the maximum allow-
able power level (V
CC(max)
, I
CC(max)
), without exceeding T
J(max)
,
at a selected R
JA
and T
A
.
Example: Reliability for V
CC
at T
A
=
150C, package LH, using a
low-K PCB.
Observe the worst-case ratings for the device, specifi cally:
R
JA
=
228 C/W, T
J(max)
=
165C, V
CC(max)
=
24 V, and
I
CC(max)
=
5
mA.
Calculate the maximum allowable power level, P
D(max)
. First,
invert equation 3:
T
max
= T
J(max)
T
A
= 165
C
150
C = 15
C
This provides the allowable increase to T
J
resulting from internal
power dissipation. Then, invert equation 2:
P
D(max)
=
T
max
R
JA
= 15C 228 C/W = 66 mW
Finally, invert equation 1 with respect to voltage:
V
CC(est)
= P
D(max)
I
CC(max)
= 66 mW 5 mA = 13 V
The result indicates that, at T
A
, the application and device can
dissipate adequate amounts of heat at voltages V
CC(est)
.
Compare V
CC(est)
to V
CC(max)
. If V
CC(est)
V
CC(max)
, then reli-
able operation between V
CC(est)
and V
CC(max)
requires enhanced
R
JA
. If V
CC(est)
V
CC(max)
, then operation between V
CC(est)
and
V
CC(max)
is reliable under these conditions.
Power Derating
11
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
Package LH, 3-Pin (SOT-23W)
Package UA, 3-Pin
12
A3230-DS
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Chopper-Stabilized Hall Effect Bipolar Switch
A3230
The products described herein are manufactured under one
or more of the following U.S. patents: 5,045,920; 5,264,783;
5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319;
5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other
patents pending.
Allegro MicroSystems, Inc. reserves the right to make, from time
to time, such de par tures from the detail spec i fi ca tions as may be
required to permit improvements in the per for mance, reliability,
or manufacturability of its products. Before placing an order, the
user is cautioned to verify that the information being relied upon is
current.
Allegro products are not authorized for use as critical compo-
nents in life-support devices or sys tems without express written
approval.
The in for ma tion in clud ed herein is believed to be ac cu rate and
reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon -
si bil i ty for its use; nor for any in fringe ment of patents or other
rights of third parties which may result from its use.
Copyright 2005 Allegro MicroSystems, Inc.
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