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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Features and Benefits
Chopper stabilization Low switchpoint drift over operating temperature range Low sensitivity to stress Factory programmed at end-of-line for optimized switchpoints On-chip protection Supply transient protection Reverse-battery protection On-board voltage regulator 3.5 to 24 V operation
Description
The A1147 and A1148 devices are two-wire, unipolar, Hall effect switches that are factory-programmed at end-of-line to optimize ultrasensitive magnetic switchpoint accuracy. These devices use a patented high frequency chopper-stabilization technique, produced using the Allegro advanced BiCMOS wafer fabrication process, to achieve magnetic stability and to eliminate offset inherent in single-element devices exposed to harsh application environments. Commonly found in a number of automotive applications, these switches are utilized to sense seat track position, seat belt buckle presence, hood/trunk latching, and shift selector position. Two-wire unipolar switches, such as the A1147 and A1148, are particularly advantageous in price-sensitive applications because they require one less wire for operation than do switches with the more traditional open-collector output. Additionally, the system designer inherently gains diagnostics because there is always output current flowing, which should be in either of two narrow ranges. Any current level not within these ranges indicates a fault condition. These devices also
Packages: 3 pin SOT23W (suffix LH), and 3 pin SIP (suffix UA)
Continued on the next page... Not to scale
Functional Block Diagram
V+ VCC
Regulator
To All Subcircuits 0.01 uF Dynamic Offset Cancellation Clock/Logic Sample and Hold Low-Pass Filter
Amp
GND Package UA Only
GND
A1147-DS, Rev. 8
A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
field of sufficient strength, and switch HIGH otherwise. Both versions are offered in two package styles. The LH is a SOT23W, miniature low-profile package for surface-mount applications. The UA is a three-lead ultramini SIP for through-hole mounting. Each package is available in a lead (Pb) free version (suffix, -T) with 100% matte tin plated leadframe. Field-programmable versions also available: A1180 and A1181.
Operating Ambient Temperature, TA (C)
Description (continued) feature on-chip transient protection and a Zener clamp to protect against overvoltage conditions on the supply line. The output currents of the A1148 switches HIGH in the presence of a south (+) polarity magnetic field of sufficient strength, and switches LOW otherwise, as in the presence of a weak field or a north (-) polarity field. The A1147 has an opposite output: the currents switch LOW in the presence of a south-polarity magnetic
Selection Guide Part Number A1147ELHLT-T A1147EUA-T A1147EUATI A1147EUATI-T A1147LLHLT-T A1147LUA-T A1147LUATI A1147LUATI-T A1148ELHLT-T A1148EUA-T A1148EUATI A1148EUATI-T A1148LLHLT-T A1148LUA-T A1148LUATI A1148LUATI-T
1Pb-based
Pb-Free1 Yes Yes - Yes Yes Yes - Yes Yes Yes - Yes Yes Yes - Yes
Packing2 Tape and Reel, 3000 pieces/reel Bulk Bag, 500 pieces/bag Tape and Reel, 2000 pieces/reel Tape and Reel, 3000 pieces/reel Bulk Bag, 500 pieces/bag Tape and Reel, 2000 pieces/reel Tape and Reel, 3000 pieces/reel Bulk Bag, 500 pieces/bag Tape and Reel, 2000 pieces/reel Tape and Reel, 3000 pieces/reel Bulk Bag, 500 pieces/bag Tape and Reel, 2000 pieces/reel
Package Surface Mount Through Hole Surface Mount Through Hole Surface Mount Through Hole Surface Mount Through Hole
Output Level in South (+) Field3
-40 to 85 Low -40 to 150
-40 to 85 High -40 to 150
variants are being phased out of the product line. a. Certain variants cited in this footnote are in production but have been determined to be LAST TIME BUY. 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: October 31, 2006. Deadlilne for receipt of LAST TIME BUY ORDERS: April 27, 2007. These variants include: A1147ELHLT, A1147EUA, A1147LLHLT, A1147LUA, A1148ELHLT, A1148EUA, and, A1148LLHLT. b. 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: A1148LUA. 2Contact Allegro for additional packing options. 3South (+) magnetic fields must be of sufficient strength.
Absolute Maximum Ratings
Characteristic Supply Voltage Reverse Supply Voltage Magnetic Flux Density Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VCC VRCC B TA TJ(max) Tstg Range E Range L Notes Rating 28 -18 Unlimited -40 to 85 -40 to 150 165 -65 to 170 Units V V 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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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Symbol VCC ICCL ICCH IRCC VZSUPPLY IZSUPPLY di/dt fC ton POS
CBYPASS = 0.01 F
ELECTRICAL CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic Supply Voltage1 Supply Current2 Reverse Supply Current Supply Zener Clamp Voltage Supply Zener Clamp Current3 Output Slew Rate4 Chopping Frequency Power-On Time5 Power-On State6,7
1V CC represents 2Relative values
Test Conditions
Min. 3.5
Typ. - - - - - - 36 200 - HIGH
Max. 24 5 17 -1.6 40 8 - - 25 -
Units V mA mA mA V mA mA/s kHz s -
B > BOP for A1147; B < BRP for A1148 B > BOP for A1148; B < BRP for A1147 VRCC = -18 V ICC = ICCL(max) + 3 mA; TA = 25C VZSUPPLY = 28 V Capacitance of the oscilloscope performing the measurement = 20 pF
2 12 - 28 - - - - -
t < ton; VCC slew rate > 25 mV/s
the generated voltage between the VCC pin and the GND pin. of B use the algebraic convention, where positive values indicate south magnetic polarity, and negative values indicate north magnetic polarity; therefore greater B values indicate a stronger south polarity field (or a weaker north polarity field, if present). 3I ZSUPPLY(max) = ICCL(max) + 3 mA. 4Measured without bypass capacitor between VCC and GND. Use of a bypass capacitor results in slower current change. 5Measured with and without bypass capacitor of 0.01 F. Adding a larger bypass capacitor causes longer Power-On Time. 6POS is defined as true only with a V CC slew rate of 25 mV / s or greater. Operation with a VCC slew rate less than 25 mV / s can permanently harm device performance. 7POS is undefined for t > t or B on RP < B < BOP .
MAGNETIC CHARACTERISTICS over the operating voltage and temperature ranges, unless otherwise specified
Characteristic Operate Point Symbol BOP A1147 A1148 A1147 A1148 Test Conditions ICC = ICCL ICC = ICCH ICC = ICCH ICC = ICCL Min. 20 Typ.* 37 Max. 80 Units G
Release Point Hysteresis
BRP BHYS
10 5
22 15
60 30
G G
BHYS = BOP - BRP
*Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions, such as TA = 25C and VCC = 12 V. Performance may vary for individual units, within the specified maximum and minimum limits.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Characteristic Data
Supply Current (Low) versus Ambient Temperature at Various Levels of VCC (A1147 and A1148)
10 8
Supply Current (High) versus Ambient Temperature at Various Levels of VCC (A1147 and A1148)
20 18
VCC 3.5 V 12.0 V 24.0 V ICCH (mA) ICCL (mA)
6 4 2 0 -50 16 14 12 10 -50
VCC 3.5 V 12.0 V 24.0 V
0
50
100
150
200
0
50
100
150
200
Ambient Temperature, TA (C)
Ambient Temperature, TA (C)
Operate Point versus Ambient Temperature at Various Levels of VCC (A1147 and A1148)
70 60 50
Switchpoint Hysteresis versus Ambient Temperature at Various Levels of VCC (A1147 and A1148)
40 35
VCC BHYS (G) 3.5 V 12.0 V 24.0 V
30 25 20 15 10 5
VCC 3.5 V 12.0 V 24.0 V
BOP (G)
40 30 20 10 0 -50
0 50 100 150 200
0 -50
0
50
100
150
200
Ambient Temperature, TA (C)
Ambient Temperature, TA (C)
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Symbol Test Conditions* Package LH, 1-layer PCB with copper limited to solder pads 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 Value Units 228 110 165 C/W C/W C/W
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic
Package Thermal Resistance
RJA
*Additional thermal information available on Allegro Web site.
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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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Functional Description
Operation The output, ICC, of the A1147 device switches low after the magnetic field at the Hall sensor exceeds the operate point threshold, BOP. When the magnetic field is reduced to below the release point threshold, BRP, the device output goes high. The differences between the magnetic operate and release point is called the hysteresis of the device, BHYS. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. The A1148 device switches with opposite polarity for similar BOP and BRP values, in comparison to the A1147 (see figure 1).
I+
ICC(H)
I+
ICC(H)
Switch to High
ICC(L) 0
Switch to High
Switch to Low
Switch to Low
ICC
ICC
BRP
BHYS
BHYS
(A) A1147
(B) A1148
Figure 1. Alternative switching behaviors are available in the A114x device family. 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).
BOP
B-
B+
0
ICC(L) B- B+
BRP
BOP
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire 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 magneticsourced 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 Low-Pass Filter
Figure 2. Chopper stabilization circuit (Dynamic Quadrature Offset Cancellation)
Sample and Hold
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Application Information
Typical Application Circuit The A114x family of devices must be protected by an external bypass capacitor, CBYP, connected between the supply, VCC, and the ground, GND, of the device. CBYP reduces both external noise and the noise generated by the chopper-stabilization function. As shown in figure 3, a 0.01 F capacitor is typical. Installation of CBYP must ensure that the traces that connect it to the A114x pins are no greater than 5 mm in length. All high-frequency interferences conducted along the supply lines are passed directly to the load through CBYP, and it serves only to protect the A114x internal circuitry. As a result, the load ECU (electronic control unit) must have sufficient protection, other than CBYP, installed in parallel with the A114x. A series resistor on the supply side, RS (not shown), in combination with CBYP, creates a filter for EMI pulses. When determining the minimum VCC requirement of the A114x device, the voltage drops across RS and the ECU sense resistor, RSENSE, must be taken into consideration. The typical value for RSENSE is approximately 100 .
ECU GND A A B Package UA Only Maximum separation 5 mm V+
VCC
B
A114x
CBYP 0.01 F
GND
B
RSENSE
Figure 3. Typical application circuit
For additional general application information, visit the Allegro Web site at www. allegromicro.com.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire 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 (2) TJ = TA + T (3) (1) Example: Reliability for VCC at TA = 150C, package UA, using minimum-K PCB. Observe the worst-case ratings for the device, specifically: RJA = 165C/W, TJ(max) = 165C, VCC(max) = 24 V, and ICC(max) = 17 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 / 165 C/W = 91 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) / ICC(max) = 91 mW / 17 mA = 5 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 = 4 mA, and RJA = 140 C/W, then: PD = VCC x ICC = 12 V x 4 mA = 48 mW T = PD x RJA = 48 mW x 140 C/W = 7C TJ = TA + T = 25C + 7C = 32C 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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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Device Qualification Program
Contact Allegro for information.
EMC (Electromagnetic Compatibility) Requirements
Contact your local representative for EMC results.
Test Name ESD - Human Body Model ESD - Machine Model Conducted Transients Direct RF Injection Bulk Current Injection TEM Cell Reference Specification AEC-Q100-002 AEC-Q100-003 ISO 7637-2 ISO 11452-7 ISO 11452-4 ISO 11452-3
Pin-out Drawings
Package LH, 3-pin SOT Package UA, 3-pin SIP
3
NC
1. VCC 2. No connection 3. GND
1
2
1. VCC 2. GND 3. GND
1
2
3
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Package LH, 3-Pin; (SOT-23W)
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
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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A1147 and A1148
Low Current Ultrasensitive Two-Wire Chopper-Stabilized Unipolar Hall Effect Switches
Package UA, 3-Pin SIP
.164 4.17 .159 4.04
C D .0805 2.04
NOM .0565 1.44 NOM D
.062 1.57 .058 1.47
D
.122 3.10 .117 2.97
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) 2004, 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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