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A3230 Chopper-Stabilized Hall-Effect Bipolar Switch
Features and Benefits
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 A3230 Hall-effect sensor is a temperature stable, stressresistant bipolar switch. This sensor is the most sensitive Hall-effect device in the Allegro(R) 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
Packages: 3 pin SOT23W (suffix LH), and 3 pin SIP (suffix UA)
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
Control
Current Limit <1
GND
3230-DS, Rev. 2
A3230
Chopper-Stabilized Hall Effect Bipolar Switch
for the L temperature range. Two A3230 package styles provide
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 -40C and 85C for the E temperature range, and -40C to 150C
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 A3230ELHLT-T A3230EUA-T A3230LLHLT-T A3230LUA-T
1Pb-based
Pb-free1 Yes Yes Yes Yes
Packing2 7-in. reel, 3000 pieces/reel Bulk, 500 pieces/bag 7-in. reel, 3000 pieces/reel Bulk, 500 pieces/bag
Mounting 3-pin SOT23W surface mount 3-pin SIP through hole 3-pin SOT23W surface mount 3-pin SIP through hole
Ambient, TA (C) -40 to 85
BRP(MIN) (G) -25
BOP(MAX) (G) 25
-40 to 150
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. for additional packing options.
2Contact Allegro
Absolute Maximum Ratings
Characteristic Supply Voltage Reverse Supply Voltage Output Off Voltage Output Current Reverse-Output Current Magnetic Flux Density Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VCC VRCC VOUT IOUTSINK IROUT B TA TJ(max) Tstg Range E Range L Notes Rating 28 -18 26.5 Internally Limited -10 Unlimited -40 to 85 -40 to 150 165 -65 to 170 Units V V V - mA G C C C C
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
OPERATING CHARACTERISTICS valid over full operating voltage and ambient temperature ranges, unless otherwise noted Characteristic Electrical Characteristics Supply Voltage1 Output Leakage Current Output On Voltage Output Current Limit Power-On Time Chopping Frequency Output Rise Time2 Output Fall Time2 Supply Current Reverse Battery Current Supply Zener Clamp Voltage Supply Zener Current3 Magnetic Characteristics4 Operate Point Release Point Hysteresis
1
Symbol VCC IOUTOFF VOUT(SAT) IOM tPO fc tr tf ICCON ICCOFF IRCC VZ IZ BOP BRP BHYS
Test Conditions Operating, TJ < 165C VOUT = 24 V, B < BRP IOUT = 20 mA, B > BOP B > BOP VCC > 3.6 V RLOAD = 820 , CS = 20 pF RLOAD = 820 , CS = 20 pF B > BOP B < BRP VRCC = -18 V ICC = 6.5 mA; TA = 25C VS = 28 V South pole adjacent to branded face of device North pole adjacent to branded face of device BOP - BRP
Min. 3.6 - - 30 - - - - - - - 28 - -10 -25 5
Typ. - - 250 - 8 200 0.2 0.2 1.6 1.6 - - - 7.5 -7.5 15
Max. 24 10 500 60 50 - 1 1 3.5 3.5 -2 - 6.5 25 10 25
Units V A mV mA s kHz s s mA mA mA V mA
G G G
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
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Electrical Characteristic Data
Supply Current (On) versus Ambient Temperature
5.0 4.0 5.0 4.0
Supply Current (On) versus Supply Voltage
ICCON (mA)
3.0 2.0 1.0 0 -50 0 50 TA (C) 100 150
ICCON (mA)
VCC (V) 24 3.6
TA (C) -40 25 150
3.0 2.0 1.0 0 0 5 10 VCC (V) 15 20 25
Supply Current (Off) versus Ambient Temperature
Supply Current (Off) versus Supply Voltage
5.0 4.0
5.0 4.0
ICCOFF (mA)
ICCOFF (mA)
VCC (V) 3.0 2.0 1.0 0 -50 0 50 TA (C) 100 150 24 3.6
TA (C) -40 25 150
3.0 2.0 1.0 0 0 5 10 VCC (V) 15 20 25
Output Voltage (On) versus Ambient Temperature
500 450 400 350 500 450 400 350
Output Voltage (On) versus Supply Voltage
VOUT(SAT) (mV)
VOUT(SAT) (mV)
300 250 200 150 100 50 0 -50 0 50 TA (C) 100 150
VCC (V) 24 3.6
300 250 200 150 100 50 0 0 5 10 VCC (V) 15 20 25
TA (C) -40 25 150
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Magnetic Characteristic Data
Operate Point versus Ambient Temperature
25 20 15 25 20 15 VCC (V) 24 3.8
Operate Point versus Supply Voltage
BOP (G)
BOP (G)
10 5 0 -5 -10 -50 0 50 TA (C) 100 150
10 5 0 -5 -10 0 5 10 VCC (V) 15 20 25
TA (C) -40 25 150
Release Point versus Ambient Temperature
10 5 0 10 5 0 VCC (V) 24 3.8
Release Point versus Supply Voltage
BRP (G)
-10 -15 -20 -25 -50 0 50 TA (C) 100 150
BRP (G)
-5
-5
TA (C) -40 25 150
-10 -15 -20 -25 0 5 10 VCC (V) 15 20 25
Hysteresis versus Ambient Temperature
25 25
Hysteresis versus Supply Voltage
20
20
BHYS (G)
BHYS (G)
VCC (V) 15 24 3.8
TA (C) 15 -40 25 150
10
10
5 -50 0 50 TA (C) 100 150
5 0 5 10 VCC (V) 15 20 25
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions* Package LH, 1-layer PCB with copper limited to solder pads Package Thermal Resistance RJA Package LH, 2-layer PCB with 0.463 in.2 of copper area each side connected by thermal vias Package UA, 1-layer PCB with copper limited to solder pads *Additional thermal information available on Allegro Web site. Value Units 228 110 165 C/W C/W C/W
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 20
VCC(max)
Maximum Allowable VCC (V)
2-layer PCB, Package LH (RJA = 110 C/W) 1-layer PCB, Package UA (RJA = 165 C/W) 1-layer PCB, Package LH (RJA = 228 C/W)
VCC(min)
120 140 160 180
40
60
80
100
Temperature (C)
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 20
Power Dissipation, PD (m W)
2l (R aye rP J C A= 11 B, P 0 ac 1-la C/ ka W (R yer PC ) ge L JA = B H 165 , Pac C/ kage W) UA
1-lay er P (R CB, JA = 228 Packag C/W e LH )
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
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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. 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. 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
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
VS
VCC
CBYP 0.1 F
RLOAD Sensor Output
A3230
VOUT
GND
(D) (A)
V+ VCC
Switch to High Switch to High Switch to Low Switch to Low
(B)
V+ VCC
Switch to High
(C)
V+ VCC
Switch to Low
VOUT
VOUT
VOUT(SAT) 0 BRP BRP B- 0 B+ 0 BOP(MAX) B- 0 BOP
VOUT(SAT) BRP(MIN) B+ 0 B- 0 BOP
VOUT
VOUT(SAT) B+
BHYS
BHYS
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 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
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 0.1F 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 ThroughHole, AN26009 All are provided in Allegro Electronic Data Book, AMS-702 and the Allegro Web site: www.allegromicro.com
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. 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. 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.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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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
Clock/Logic Hall Element Amp
Sample and Hold
Figure 2. Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation)
Low-Pass Filter
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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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, RJA, 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, RJC, is relatively small component of RJA. 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 x IIN T = PD x RJA TJ = TA + T (1) (2) (3)
Example: Reliability for VCC at TA = 150C, package LH, using a low-K PCB. Observe the worst-case ratings for the device, specifically: RJA = 228 C/W, TJ(max) = 165C, 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 / RJA = 15C / 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 RJA. 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= 25C, VCC = 12 V, ICC = 1.5 mA, and RJA = 165 C/W, then: PD = VCC x ICC = 12 V x 1.5 mA = 18 mW T = PD x RJA = 18 mW x 165 C/W = 3C TJ = TA + T = 25C + 3C = 28C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RJA and TA.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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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
A
A 1.49 .059 NOM 8 0 0.20 .008 0.08 .003
3
B
B
2.10 .083 1.85 .073 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] 3X 0.10 [.004] C 3X 0.50 .020 0.30 .012 0.20 [.008] M C A B 0.95 .037 1.90 .075
A
0.96 .038
A NOM
0.60 .024 0.25 .010
1
2 0.25 .010 SEATING PLANE 1.17 .046 0.75 .030 0.15 .006 0.00 .000 C SEATING PLANE GAUGE PLANE
Pin-out Drawings
Package LH
3
Package UA
1
2
1
2
3
Terminal List
Name VCC VOUT GND Description Connects power supply to chip Output from circuit Ground Number Package LH 1 2 3 Package UA 1 3 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A3230
Chopper-Stabilized Hall Effect Bipolar Switch
Package UA, 3-Pin SIP
.164 4.17 .159 4.04
C D
.0805 2.04 NOM
.062 1.57 .058 1.47
D
.122 3.10 .117 2.97
.0565 1.44 NOM D
B
.085 2.16 MAX
.031 0.79 REF A
.640 16.26 .600 15.24
.017 0.44 .014 0.35
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 (c) 2005, 2006 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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