Allegro A3230 Chopper-stabilized hall-effect bipolar switch Datasheet

A3230
Chopper-Stabilized Hall-Effect Bipolar Switch
Features and Benefits
Description
▪ 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, stressresistant 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.
Packages: 3 pin SOT23W (suffix LH), and
3 pin SIP (suffix UA)
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
Continued on the next page…
Not to scale
Functional Block Diagram
VCC
Regulator
Low-Pass
Filter
Amp
Sample and Hold
Dynamic Offset
Cancellation
To All Subcircuits
VOUT
Control
Current Limit
<1Ω
GND
3230-DS, Rev. 2
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Description (continued)
diminished or removed, to ensure that the device switches, Allegro
recommends using magnets of both polarities and of sufficient
strength in the application.
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 SOT23-W, 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.
Selection Guide
Part Number
Pb-free1
A3230ELHLT-T
A3230EUA-T
A3230LLHLT-T
A3230LUA-T
Yes
Yes
Yes
Yes
Packing2
Mounting
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
7-in. reel, 3000 pieces/reel
Bulk, 500 pieces/bag
3-pin SOT23W surface mount
3-pin SIP through hole
3-pin SOT23W surface mount
3-pin SIP through hole
Ambient, TA
(°C)
BRP(MIN)
(G)
BOP(MAX)
(G)
–25
25
–40 to 85
–40 to 150
1Pb-based
variants are being phased out of the product line. Certain variants cited in this footnote are in production but have been determined to be NOT FOR NEW DESIGN.
This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications
because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006. These variants include: A3230ELHLT, A3230EUA,
A3230LLHLT, and A3230LUA.
2Contact Allegro
for additional packing options.
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Units
Supply Voltage
VCC
28
V
Reverse Supply Voltage
VRCC
–18
V
VOUT
26.5
V
IOUTSINK
Internally Limited
–
Output Off Voltage
Output Current
IROUT
–10
mA
Magnetic Flux Density
Reverse-Output Current
B
Unlimited
G
Operating Ambient Temperature
TA
Maximum Junction Temperature
Storage Temperature
Range E
–40 to 85
ºC
Range L
–40 to 150
ºC
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
2
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
3.5
mA
ICCOFF
B < BRP
–
1.6
3.5
mA
VRCC = –18 V
–
–
–2
mA
VZ
ICC = 6.5 mA; TA = 25°C
28
–
–
V
IZ
VS = 28 V
–
–
6.5
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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
3
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)
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115 Northeast Cutoff, Box 15036
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4
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)
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Symbol
Test Conditions*
RθJA
Package Thermal Resistance
Value Units
Package LH, 1-layer PCB with copper limited to solder pads
228
ºC/W
Package LH, 2-layer PCB with 0.463 in.2 of copper area each side
connected by thermal vias
110
ºC/W
Package UA, 1-layer PCB with copper limited to solder pads
165
ºC/W
*Additional thermal information available on Allegro Web site.
Maximum Allowable VCC (V)
Power Derating Curve
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
VCC(max)
2-layer PCB, Package LH
(RθJA = 110 ºC/W)
1-layer PCB, Package UA
(RθJA = 165 ºC/W)
1-layer PCB, Package LH
(RθJA = 228 ºC/W)
20
40
60
80
100
VCC(min)
120
140
160
180
Temperature (ºC)
Power Dissipation, PD (m W)
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
2l
(R aye
rP
θJ
C
A =
11 B, P
0 º ac
1-la
C/ ka
W
(R yer PC
) ge L
θJA =
B
H
165 , Pac
ºC/ kage
W)
UA
1-lay
er P
(R
CB,
θJA =
228 Packag
ºC/W
e LH
)
20
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
6
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.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
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7
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
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
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)
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9
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)
ΔT = PD × RθJA
(2)
TJ = TA + ΔT
(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:
ΔTmax = 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) = ΔTmax ÷ 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
ΔT = PD × RθJA = 18 mW × 165 °C/W = 3°C
TJ = TA + ΔT = 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
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Package LH, 3-Pin SOT23-W
3.00 .118
2.70 .106
0.15 [.006] M C A B
3.04 .120
2.80 .110
3
A
A
1.49 .059
NOM
8º
0º
B
B
0.20 .008
0.08 .003
2.10 .083
1.85 .073
A
Preliminary dimensions, for reference only
Dimensions in millimeters
U.S. Customary dimensions (in.) in brackets, for reference only
(reference JEDEC TO-236 AB, except case width and terminal tip-to-tip)
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
A Hall element (not to scale)
B Active Area Depth 0.28 [.011]
0.96 .038
0.60 .024
0.25 .010
A NOM
1
2
0.25 .010
3X
C
SEATING
PLANE
0.10 [.004] C
3X 0.50 .020
0.30 .012
SEATING PLANE
GAUGE PLANE
1.17 .046
0.75 .030
0.20 [.008] M C A B
0.15 .006
0.00 .000
0.95 .037
1.90 .075
Pin-out Drawings
Package UA
Package LH
3
1
1
2
2
3
Terminal List
Name
VCC
Description
Number
Package LH
Package UA
Connects power supply to chip
1
1
VOUT
Output from circuit
2
3
GND
Ground
3
2
11
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Package UA, 3-Pin SIP
.164 4.17
.159 4.04
C
D
.122 3.10
.117 2.97
.0805 2.04
NOM
.062 1.57
.058 1.47
D
.0565 1.44
NOM D
B
.085 2.16
MAX
.031 0.79
REF
A
.017 0.44
.014 0.35
.640 16.26
.600 15.24
1
2
3
.019 0.48
.014 0.36
.050 1.27
NOM
Dimensions in inches
Metric dimensions (mm) in brackets, for reference only
A Dambar removal protrusion (6X)
B Ejector mark on opposite side
C Active Area Depth .0195 [0.50] NOM
D Hall element (not to scale)
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, 2006 Allegro MicroSystems, Inc.
12
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com