Allegro A3230ELHLT Chopper-stabilized hall-effect bipolar switch Datasheet

A3230
Chopper-Stabilized
Hall-Effect Bipolar Switch
GND
Package LH, 3-pin Surface Mount
3
1
3
2
VCC
VOUT
2
1
Package UA, 3-pin SIP
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 cancellation 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 amplifier, 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 field of
sufficient strength and switches off in a north polarity magnetic field of sufficient
strength. Because the output state is not defined if the magnetic field is diminished
or removed, to ensure that the device switches, Allegro recommends using magnets of both polarities and of sufficient strength in the application.
1
2
3
VCC
GND
VOUT
The A3230 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. Two A3230 package styles provide magnetically optimized solutions
for most applications. Package LH is a SOT23W, a miniature low-profile
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 2
3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 28 V
Reverse-Supply Voltage, VRCC ........................ –18 V
Output Off Voltage, VOUT ............................... 26.5 V
Output Current, IOUTSINK ........... Internally Limited
Reverse-Output Current, IROUT ....................–10 mA
Magnetic Flux Density, B .........................Unlimited
Operating Temperature
Ambient, TA, Range E.................. –40ºC to 85ºC
Ambient, TA, Range L................ –40ºC to 150ºC
Maximum Junction, TJ(MAX) ......................165ºC
Storage Temperature, TS .................. –65ºC to 170ºC
A3230-DS
Features and Benefits
Chopper stabilization
Output short circuit protection
Superior temperature stability
Solid state reliability
Extremely low switchpoint drift
Small size
Insensitive to physical stress
Reverse battery protection
Robust EMC capability
High ESD ratings (HBM)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Product Selection Guide
Part Number
Pbfree
Packing*
Ambient, TA
(°C)
Mounting
A3230ELHLT
–
7-in. reel, 3000 pieces/reel
A3230ELHLT-T
Yes
A3230EUA
–
Bulk, 500 pieces/bag
A3230EUA-T
Yes
A3230LLHLT
–
7-in. reel, 3000 pieces/reel
A3230LLHLT-T
Yes
A3230LUA
–
Bulk, 500 pieces/bag
A3230LUA-T
Yes
*Contact Allegro for additional packing options.
BRP(MIN)
(G)
BOP(MAX)
(G)
–25
25
3-pin SOT23W surface mount
–40 to 85
3-pin SIP through hole
3-pin SOT23W surface mount
–40 to 150
3-pin SIP through hole
Functional Block Diagram
VCC
Regulator
Amp
Low-Pass
Filter
Sample and Hold
Dynamic Offset
Cancellation
To All Subcircuits
VOUT
Control
Current Limit
<1Ω
GND
Terminal List
Name
Description
Number
Package LH
Package UA
Connects power supply to chip
1
1
VOUT
Output from circuit
2
3
GND
Ground
3
2
VCC
2
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
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 Voltage1
Output Leakage Current
VCC
Operating, TJ < 165°C
3.6
–
24
V
IOUTOFF
VOUT = 24 V, B < BRP
–
–
10
µA
VOUT(SAT)
IOUT = 20 mA, B > BOP
–
250
500
mV
Output Current Limit
IOM
B > BOP
30
–
60
mA
Power-On Time
tPO
VCC > 3.6 V
Output On Voltage
–
8
50
µs
–
200
–
kHz
RLOAD = 820 Ω, CS = 20 pF
–
0.2
1
µs
RLOAD = 820 Ω, CS = 20 pF
–
0.2
1
µs
ICCON
B > BOP
–
1.6
5
mA
ICCOFF
B < BRP
–
1.6
5
mA
VRCC = –18 V
–
–
–2
mA
VZ
ICC = 8 mA; TA = 25°C
28
–
–
V
IZ
VS = 28 V
–
–
8
mA
Chopping Frequency
fc
Output Rise Time2
tr
Output Fall Time2
tf
Supply Current
Reverse Battery Current
Supply Zener Clamp Voltage
Supply Zener
Current3
IRCC
Magnetic Characteristics4
Operate Point
BOP
South pole adjacent to branded face of device
–10
7.5
25
G
Release Point
BRP
North pole adjacent to branded face of device
–25
–7.5
10
G
Hysteresis
BHYS
BOP – BRP
5
15
25
G
1
Maximum voltage must be adjusted for power dissipation and junction temperature, see Power Derating section.
2 C = oscilloscope probe capacitance.
S
3 Maximum current limit is equal to the maximum I
CC(MAX) + 3 mA.
4 Magnetic flux density, B, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields.
This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated
by the absolute value of B, and the sign indicates the polarity of the field (for example, a –100 G field and a 100 G field have equivalent strength, but
opposite polarity).
DEVICE QUALIFICATION PROGRAM
Contact Allegro for information.
EMC (Electromagnetic Compatibility) REQUIREMENTS
Contact Allegro for information.
3
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Electrical Characteristic Data
Supply Current (On) versus Ambient Temperature
Supply Current (On) versus Supply Voltage
5.0
5.0
4.0
VCC (V)
3.0
24
3.6
2.0
ICCON (mA)
ICCON (mA)
4.0
1.0
3.0
–40
25
150
2.0
1.0
0
–50
TA (°C)
0
0
50
TA (°C)
100
150
0
25
4.0
VCC (V)
3.0
24
3.6
2.0
ICCOFF (mA)
ICCOFF (mA)
20
5.0
4.0
TA (°C)
–40
25
150
3.0
2.0
1.0
1.0
0
0
0
50
TA (°C)
100
0
150
5
10
15
20
25
VCC (V)
Output Voltage (On) versus Ambient Temperature
Output Voltage (On) versus Supply Voltage
500
500
450
450
400
400
350
350
300
VCC (V)
250
24
3.6
200
150
VOUT(SAT) (mV)
VOUT(SAT) (mV)
15
Supply Current (Off) versus Supply Voltage
5.0
TA (°C)
300
–40
25
150
250
200
150
100
100
50
50
0
–50
10
VCC (V)
Supply Current (Off) versus Ambient Temperature
–50
5
0
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
4
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Magnetic Characteristic Data
Operate Point versus Ambient Temperature
Operate Point versus Supply Voltage
25
25
20
20
15
10
VCC (V)
5
24
3.8
TA (°C)
10
BOP (G)
BOP (G)
15
–40
25
150
5
0
0
-5
-5
-10
-10
–50
0
50
TA (°C)
100
150
0
15
20
25
Release Point versus Supply Voltage
10
10
5
5
0
-5
VCC (V)
-10
24
3.8
BRP (G)
0
BRP (G)
10
VCC (V)
Release Point versus Ambient Temperature
TA (°C)
-5
–40
25
150
-10
-15
-15
-20
-20
-25
-25
–50
0
50
TA (°C)
100
0
150
5
10
15
20
25
VCC (V)
Hysteresis versus Ambient Temperature
Hysteresis versus Supply Voltage
25
25
20
20
VCC (V)
24
3.8
15
10
BHYS (G)
BHYS (G)
5
TA (°C)
–40
25
150
15
10
5
5
–50
0
50
TA (°C)
100
150
0
5
10
15
20
25
VCC (V)
5
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
RθJA
Package Thermal Resistance
Test Conditions
Package LH, minimum-K PCB (single-sided with
copper limited to solder pads)
Package LH, low-K PCB (double-sided with
0.926 in2 copper area)
Package UA, minimum-K PCB (single-sided with
copper limited to solder pads)
Value
Units
110
ºC/W
228
ºC/W
165
ºC/W
Maximum Allowable V CC (V)
Power Derating Curve
TJ(max) = 165°C; ICC = ICC(max)
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
V CC(max)
Low-K PCB, Package LH
(R θJA= 110 °C/W)
Minimum-K PCB, Package UA
(R θJA= 165 °C/W)
Minimum-K PCB, Package LH
(R θJA= 228 °C/W)
V CC(min)
20
40
60
80
100
120
140
160
180
Temperature (°C)
Power Dissipation, P D (mW)
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
Low-K PCB, Package LH
(R JA = 110 °C/W)
Min-K PCB, Package UA
(R JA = 165 °C/W)
Min-K PCB, Package LH
(R JA = 228 °C/W)
20
40
60
80
100
120
140
160
180
Temperature (°C)
6
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Functional Description
Operation
The output of these devices switches low (turns on) when a
magnetic field perpendicular to the Hall sensor exceeds the
operate point threshold, BOP. After turn-on, the output voltage
is VOUT(SAT). The output transistor is capable of sinking current
up to the short circuit current limit, IOM, which is a minimum of
30 mA. When the magnetic field is reduced below the release
point, BRP, the device output goes high (turns off). The difference in the magnetic operate and release points is the hysteresis,
BHYS, of the device. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical
vibration and electrical noise.
field of the opposite polarity and of sufficient strength causes
it to switch. The hysteresis of latch mode behavior is shown in
panel A of figure 1.
In contrast to latching, when a device exhibits unipolar switching, it only responds to a south magnetic field. The field must
be of sufficient strength, > BOP , for the device to operate. When
the field is reduced beyond the BRP level, the device switches
back to the high state, as shown in panel B of figure 1. Devices
There are three switching modes for bipolar devices, referred to
as latch, unipolar switch, and negative switch. Mode is determined by the switchpoint characteristics of the individual device.
Note that, as shown in figure 1, these switchpoints can lie in
either north or south polarity ranges. The values of the magnetic
parameters for the A3230 are specified in the Magnetic Characteristics table, on page 3.
VS
VCC
CBYP
0.1 µF
A3230
RLOAD
Sensor Output
VOUT
GND
Bipolar devices typically behave as latches (although these
devices are not guaranteed to do so). In this mode, magnetic
fields of opposite polarity and equivalent strengths are needed
to switch the output. When the magnetic fields are removed
(B → 0) the device remains in the same state until a magnetic
(D)
(A)
(B)
V+
V+
Switch to High
Switch to High
VOUT
BHYS
B+
B–
BRP(MIN)
BRP
B– 0
VOUT(SAT)
0
BOP
BHYS
B+
VOUT(SAT)
0
BOP(MAX)
0
BOP
B–
BRP
VOUT(SAT)
0
VCC
Switch to Low
VOUT
VCC
Switch to Low
Switch to Low
Switch to High
VCC
VOUT
V+
(C)
0
B+
BHYS
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 BHYS band incorporates B= 0), panel B shows unipolar switch behavior (the
BHYS band is more positive than B = 0), and panel C shows negative switch behavior (the BHYS band is more negative than B = 0). Bipolar devices,
such as the A3230, can operate in any of the three modes.
7
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
exhibiting negative switch behavior operate in a similar but
opposite manner. A north polarity field of sufficient strength,
> BRP , (more north than BRP) is required for operation, although
the result is that VOUT switches high, as shown in panel C. When
the field is reduced beyond the BOP level, the device switches
back to the low state.
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 figure 1, a 0.1µF capacitor is typical.
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 magnetic fields, as in a ring magnet.
Extensive applications information on magnets and Hall-effect
sensors is available in:
Bipolar devices adopt an indeterminate output state when
powered-on in the absence of a magnetic field or in a field that
lies within the hysteresis band of the device. The correct state is
attained after the first excursion beyond BOP or BRP.
For more information on Bipolar switches, refer to Application
Note 27705, Understanding Bipolar Hall Effect Sensors.
• 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 ThroughHole, AN26009
All are provided in Allegro Electronic Data Book, AMS-702 and
the Allegro Web site: www.allegromicro.com
8
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
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 difficult to process the signal while
maintaining an accurate, reliable output over the specified operating 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 modulationdemodulation process. The undesired offset signal is separated
from the magnetic-field-induced signal in the frequency domain,
through modulation. The subsequent demodulation acts as a
modulation process for the offset, causing the magnetic-fieldinduced signal to recover its original spectrum at baseband,
while the dc offset becomes a high-frequency signal. The magnetic-field-induced signal then can pass through a low-pass filter,
while the modulated dc offset is suppressed. This configuration
is illustrated in figure 2.
The chopper stabilization technique uses a 200 kHz high-frequency 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 desensitizes 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
amplifiers in combination with high-density logic integration and
sample-and-hold circuits.
The repeatability of magnetic-field-induced switching is affected
slightly by a chopper technique. However, the Allegro highfrequency 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 fields; for
example, speed sensing of ring-magnet targets. For such applications, Allegro recommends its digital sensor families with lower
sensitivity to jitter. For more information on those devices,
contact your Allegro sales representative.
Regulator
Amp
Low-Pass
Filter
Hall Element
Sample and
Hold
Clock/Logic
Figure 2. Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation)
9
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Power Derating
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the
application. This section presents a procedure for correlating
factors affecting operating TJ. (Thermal data is also available on
the Allegro MicroSystems Web site.)
The Package Thermal Resistance, RθJA, is a figure of merit summarizing 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, RθJC, is
relatively small component of RθJA. Ambient air temperature,
TA, and air motion are significant external factors, damped by
overmolding.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD.
PD = VIN × IIN
(1)
∆T = PD × RθJA
(2)
TJ = TA + ∆T
(3)
Example: Reliability for VCC at TA = 150°C, package LH, using a
low-K PCB.
Observe the worst-case ratings for the device, specifically:
RθJA = 228 °C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 5 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
∆Tmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = ∆Tmax ÷ RθJA = 15°C ÷ 228 °C/W = 66 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 66 mW ÷ 5 mA = 13 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced
RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 1.5 mA, and RθJA = 165 °C/W, then:
PD = VCC × ICC = 12 V × 1.5 mA = 18 mW
∆T = PD × RθJA = 18 mW × 165 °C/W = 3°C
TJ = TA + ∆T = 25°C + 3°C = 28°C
A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max),
at a selected RθJA and TA.
10
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Package LH, 3-Pin (SOT-23W)
Package UA, 3-Pin
11
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
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 departures from the detail specifications as may be
required to permit improvements in the performance, 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 components in life-support devices or systems without express written
approval.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other
rights of third parties which may result from its use.
Copyright © 2005 Allegro MicroSystems, Inc.
12
A3230-DS
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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