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A3241 and A3242
Chopper-Stabilized Unipolar Hall-Effect Switches
Package LH, 3-pin Surface Mount
GND
3
The A3241 and A3242 integrated circuits are unipolar Hall-effect switches with digital outputs. These sensors are suited for operation over extended temperature ranges, up to +150C. Superior high-temperature performance is made possible through an Allegro(R) patented dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature excursions, and thermal stress. The A3241 and A3242 Hall-effect switches include 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 integrated voltage regulator permits operation from 3.6 to 24 V. The unipolar family members operate with a sufficient south polarity field only, turning off in the absence of such a south polarity field. The A3241 and A3242 are rated for operation between the ambient temperatures -40C and 85C for the E temperature range, and -40C to 150C for the L temperature range. The small geometries of the BiCMOS process allow these devices to be provided in ultrasmall packages. The package styles available provide magnetically optimized solutions for most applications. Package LH is an 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
1 2
3
Package UA, 3-pin SIP
1
2
VOUT
GND
VCC
VOUT
3
VCC
12 3
Features and Benefits
Chopper stabilization Output short circuit protection Solid state reliability Small size Robust EMC capability High ESD ratings (HBM) Superior temperature stability Extremely low switchpoint drift Insensitive to physical stress Reverse battery protection
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 28 V Reverse-Supply Voltage, VRCC ........................ -18 V Reverse-Supply Current, IRCC ........................-2 mA Output Off Voltage, VOUT .................................. 28 V Output Current, IOUTSINK ........... Internally Limited Magnetic Flux Density, B .........................Unlimited Operating Temperature Ambient, TA, Range E.................. -40C to 85C Ambient, TA, Range L................ -40C to 150C Maximum Junction, TJ(MAX) ......................165C Storage Temperature, TS .................. -65C to 170C
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
Product Selection Guide
Part Number Pbfree Packing* Mounting 3-pin SOT23W surface mount -40 to 85 3-pin SIP through hole 40 3-pin SOT23W surface mount -40 to 150 3-pin SIP through hole 3-pin SOT23W surface mount -40 to 85 3-pin SIP through hole 110 3-pin SOT23W surface mount -40 to 150 3-pin SIP through hole 200 135 Ambient, TA (C) BRP(MIN) (G) BOP(MAX) (G) A3241ELHLT - 7-in. reel, 3000 pieces/reel A3241ELHLT-T Yes A3241EUA - Bulk, 500 pieces/bag A3241EUA-T Yes A3241LLHLT - 7-in. reel, 3000 pieces/reel A3241LLHLT-T Yes A3241LUA - Bulk, 500 pieces/bag A3241LUA-T Yes A3242ELHLT - 7-in. reel, 3000 pieces/reel A3242ELHLT-T Yes A3242EUA - Bulk, 500 pieces/bag A3242EUA-T Yes A3242LLHLT - 7-in. reel, 3000 pieces/reel A3242LLHLT-T Yes A3242LUA - Bulk, 500 pieces/bag A3242LUA-T Yes *Contact Allegro for additional packing options.
Functional Block Diagram
VCC
Regulator To All Subcircuits Sample and Hold Dynamic Offset Cancellation Low-Pass Filter
VOUT
Amp
Amp
Control
Current Limit <1
GND
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
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
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 VZSupply IZSupply
Test Conditions Operating, TJ < 165C VOUT = 24 V, B < BRP IOUT = 20 mA, B > BOP B > BOP VCC > VCC(MIN) 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 A3241 A3242 A3241 A3242 A3241 A3242 BOP - BRP
Min. 3.6 - - 30 - - - - - - - 28 - 50 120 40 110 10 10
Typ. - - - - - 200 - - 1.5 1.5 - - - 95 150 70 125 25 25
Max. 24 10 500 60 50 - 1 1 3.5 3.5 -2 - 6.5 135 200 110 190 42 40
Units V A mV mA s kHz s s mA mA mA V mA
G G G G G G
BOP BRP BHYS
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.
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
3
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
Characteristic Data
Supply Current (On) versus Ambient Temperature
5.0 4.0
ICCON (mA)
Supply Current (On) versus Supply Voltage
5.0 4.0 VCC (V) 24 3.6 3.0 2.0 1.0 0 TA (C) -40 25 150
ICCON (mA)
3.0 2.0 1.0 0.0 -50 0 50 TA (C) 100 150
0
5
10 VCC (V)
15
20
25
Supply Current (Off) versus Ambient Temperature
5.0 4.0
ICCOFF (mA)
Supply Current (Off) versus Supply Voltage
5.0 4.0 VCC (V) 24 3.6 3.0 2.0 1.0 0 TA (C) -40C -40 25C 25 150C 150
ICCOFF (mA)
3.0 2.0 1.0 0.0 -50 0 50 TA (C) 100 150
0
5
10 VCC (V)
15
20
25
Output Voltage (On) versus Ambient Temperature
500 450 400
V OUT(SAT) (mV)
Output Voltage (On) versus Supply Voltage
500 450 400 VCC (V) 24 3.6
VOUT(SAT) (mV)
350 300 250 200 150 100 50 0 -50 0 50 TA (C) 100 150
350 300 250 200 150 100 50 0 0 5 10 VCC (V) 15 20 25 TA (C) 150C -40 25C 25 -40C 150
Continued on the next page...
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
Operate Point versus Ambient Temperature (A3241)
130 120 110
BOP (G) BOP (G)
Operate Point versus Supply Voltage (A3241)
130 120 110 VCC (V) 24 3.6 100 90 80 70 60 50 TA (C) -40 25 150
100 90 80 70 60 50 -50 0 50 TA (C) 100 150
0
5
10 VCC (V)
15
20
25
110 100 90
BRP [G]
Release Point versus Ambient Temperature (A3241)
Release Point versus Supply Voltage (A3241)
110 100 90 VCC (V) 24 3.6
BRP (G)
80 70 60 50 40 -50 0 50 TA (C) 100 150
80 70 60 50 40 0 5 10 VCC (V) 15 20 25
TA (C) -40 25 150
Hysteresis versus Ambient Temperature (A3241)
40 35
BHYS (G) BHYS (G)
Hysteresis versus Supply Voltage (A3241)
40 35 VCC (V) 24 3.6 30 25 20 15 10 TA (C) -40 25 150
30 25 20 15 10 -50 0 50 TA (C) 100 150
0
5
10 VCC (V)
15
20
25
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
5
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
200 190 180
BOP (G)
Operate Point versus Ambient Temperature (A3242)
Operate Point versus Supply Voltage (A3242)
200 190 180 VCC (V) 24 3.6
BOP (G)
170 160 150 140 130 120 -50 0 50 TA (C) 100 150
170 160 150 140 130 120 0 5 10 VCC (V) 15 20 25
TA (C) -40 25 150
Release Point versus Ambient Temperature (A3242)
190 180 170
BRP (G) BRP (G)
Release Point versus Supply Voltage (A3242)
190 180 170 VCC (V) 24 3.6 160 150 140 130 120 110 TA (C) -40 25 150
160 150 140 130 120 110 -50 0 50 TA (C) 100 150
0
5
10 VCC (V)
15
20
25
Hysteresis versus Ambient Temperature (A3242)
40 35 30
BHYS (G)
Hysteresis versus Supply Voltage (A3242)
40 35 VCC (V) 24 3.6 30
BHYS (G)
25 20 15 10 -50 0 50 TA (C) 100 150
25 20 15 10 0 5 10 VCC (V) 15 20 25
TA (C) -40 25 150
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
6
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions Package LH-3, 1-layer PCB with copper limited to solder pads Package LH-3, 2-layer PCB with 0.926 in2 on each side, connected by thermal vias Package UA, 1-layer PCB with copper limited to solder pads Value 110 228 165 Units C/W C/W C/W
Package Thermal Resistance
RJA
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 V CC(max)
Maximum Allowable V CC (V)
1-layer PCB, Package LH (R JA= 110 C/W) 1-layer PCB, Package UA (R JA= 165 C/W) 2-layer PCB, Package LH (R JA= 228 C/W) V CC(min) 40 60 80 100 120 140 160 180 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)
1l (R aye rP J C A= 11 B, P 0 ac 1-la C/ ka W (R yer P ) ge L CB JA = H , Pa 165 C/ ckage W) UA
2-la y (R er PCB , JA = 228 Packa C/W ge L H )
40
60
80 100 120 Temperature (C)
140
160
180
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
7
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
Functional Description
Operation The output of these devices switches low (turns on) when a magnetic field (south polarity) 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. Powering-on the device in the hysteresis region, less than BOP and higher than BRP, allows an indeterminate output state. The correct state is attained after the first excursion beyond BOP or BRP. 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
(A)
V+
VS
(B)
VCC
Switch to High
VCC
CBYP 0.1 F
RLOAD VOUT Sensor Output
Switch to Low
VCC
A324x
0
VOUT(SAT)
GND
BRP
B-
0
B+
BOP
BHYS
Figure 1: Switching Behavior of Unipolar Switches. In Panel A, on the horizontal axis, the B+ direction indicates increasing south polarity magnetic field strength, and the B- direction indicates decreasing south polarity field strength (including the case of increasing north polarity). This behavior can be exhibited when using a circuit such as that shown in panel B.
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
8
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
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
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
9
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
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 = 65.8 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) / ICC(max) = 65.8 mW / 5 mA = 13.2 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.
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
10
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
Package LH, 3-Pin (SOT-23W)
Package UA, 3-Pin
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
11
A3241 and A3242
Chopper-Stabilized Unipolar Hall Effect Switches
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 Allegro MicroSystems, Inc.
A3241-DS, Rev. 2
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
12

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