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ACS704ELC-015
Fully Integrated, Hall Effect-Based Linear Current Sensor with Voltage Isolation and a Low-Resistance Current Conductor
Package LC The Allegro ACS704 family of current sensors provides economical and precise solutions for current sensing in industrial, automotive, commercial, and communications systems. The device package allows for easy implementation by the customer. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection.
8 7 6 5
1 2 3 4
Pin 1: Pin 2: Pin 3: Pin 4: IP+ IP+ IP- IP-
Pin 5: GND Pin 6: VOUT Pin 7: VOUT Pin 8: VCC
The device consists of a precision, low-offset linear Hall sensor circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field which is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy is optimized through the close proximity of the magnetic signal to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC, which is programmed for accuracy at the factory. The output of the device has a positive slope (>VCC / 2) when an increasing current flows through the primary copper conduction path (from pins 1 and 2, to pins 3 and 4), which is the path used for current sensing. The internal resistance of this conductive path is typically 1.5 m, providing low power loss. The thickness of the copper conductor allows survival of the device at up to 3x overcurrent conditions. The terminals of the conductive path are electrically isolated from the sensor leads (pins 5 through 8). This allows the ACS704 family of sensors to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. The ACS704 is provided in a small, surface mount SOIC8 package. The leadframe is plated with 100% matte tin, which is compatible with standard lead (Pb) free printed circuit board assembly processes. Internally, the flip-chip uses high-temperature Pb-based solder balls, currently exempt from RoHS and WEEE. The device is fully calibrated prior to shipment from the factory.
Nominal Operating Temperature, TA Range E............................................ -40 to 85C Overcurrent Transient Tolerance*, IP ................ 60 A
*100
total pulses, 250 ms duration each, applied at a rate of 1 pulse every 100 seconds.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC .......................................... 16 V Reverse Supply Voltage, VRCC ........................ -16 V Output Voltage, VOUT ........................................ 16 V Reverse Output Voltage, VROUT...................... -0.1 V Output Current Source, IOUT(Source) ................. 3 mA Output Current Sink, IOUT(Sink) .......................10 mA Operating Temperature, Maximum Junction, TJ(max)....................... 165C Storage Temperature, TS ...................... -65 to 170C
Features and Benefits
* * * * * * * * * * * * Small footprint, low-profile SOIC8 package 1.5 m internal conductor resistance Excellent replacement for sense resistors 800 VRMS minimum isolation voltage beween pins 1-4 and 5-8 4.5 to 5.5 V, single supply operation 50 kHz bandwidth 100 mV/A output sensitivity and 20 A dynamic range Output voltage proportional to ac and dc currents Factory-trimmed for accuracy Extremely stable output offset voltage Near-zero magnetic hysteresis Ratiometric output from supply voltage
TUV America Certificate Number: U8V 04 12 54214 005
Use the following complete part number when ordering:
Part Number
ACS704ELC-015
Package
SOIC8 surface mount
ACS704015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Functional Block Diagram
+5 V Pin 3 Pin 4 IP- IP- VCC Pin 8
Voltage Regulator To all subcircuits
Dynamic Offset Cancellation
Amp
Filter
VOUT Pin 7
Out
VOUT Pin 6
0.1 F
Gain
Temperature Coefficient Trim Control
Offset
IP+ IP+ Pin 1 Pin 2
GND Pin 5
2
ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
ELECTRICAL CHARACTERISTICS, over operating ambient temperature range unless otherwise stated
Characteristic Symbol Test Conditions Min. 1 Primary Sensed Current IP -15 Supply Voltage VCC 4.5 Supply Current ICC VCC = 5.0 V, output open 5 IOUT = 1.2 mA - Output Resistance ROUT Output Capacitance Load CLOAD VOUT to GND - VOUT to GND 4.7 Output Resistive Load RLOAD Primary Conductor Resistance RPRIMARY TA = 25C - Isolation Voltage VISO Pins 1-4 and 5-8; 60 Hz, 1 minute 800 PERFORMANCE CHARACTERISTICS, TA = -40C to 85C, VCC = 5 V unless otherwise specified Propagation Time tPROP IP =15 A, TA = 25C - - Response Time tRESPONSE IP =15 A, TA = 25C Rise Time Frequency Bandwidth tr f IP =15 A, TA = 25C -3 dB, TA = 25C; IP is 10 A peak-topeak; no external filter Over full range of IP , IP applied for 5 ms; TA = 25C Over full range of IP , IP applied for 5 ms; TA = -40 to 85C Peak-to-peak, TA = 25C, no external filter Root Mean Square, TA = 25C, no external filter Over full range of IP , IP applied for 5 ms; TA = -40 to 85C Over full range of IP , IP applied for 5 ms; TA = -40 to 85C IP = 0 A, TA = 25C IP = 0 A, TA = 25C IP = 0 A, TA = -40 to 85C IP = 0 A, after excursion of 15 A; TA = -40 to 85C IP =15 A , IP applied for 5 ms; TA = 25C IP = 10 A , IP applied for 5 ms; TA = -40 to 85C IP = 15 A , IP applied for 5 ms; TA = -40 to 85C - - - 94 - - - 98 - -15 -50 - - - - Typ. - 5.0 8 1 - - 1.5 1200 4 8 9 50 100 - 70 12.5 1 100 VCC / 2 - - 0.01 1.5 - - Max. 15 5.5 10 2 10 - - - - - - - - 106 - - 3.5 102 - 15 50 0.05 - 6.0 8.4 Units A V mA nF k m V s s s kHz mV/A mV/A mV mV % % V mV mV A % % %
Sensitivity
Sens
Noise
VNOISE
Nonlinearity Symmetry Zero Current Output Voltage Electrical Offset Voltage Magnetic Offset Error
ELIN ESYM VOUT(Q) VOE IERROM
Total Output Error2
ETOT
1Device may be operated at higher primary current, I , and Ambient Temperature, T , levels, provided that the Maximum Junction Temperature, T P A J(max), is not exceeded. 2Percentage of I , with I = 15 A; Output filtered. Up to a 2.0% shift in E P P TOT may be observed at end-of-life for this device.
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Typical Performance Characteristics
Supply Current versus Ambient Temperature VCC = 5 V
10.0 9.6 9.2 8.8
ICC (mA)
8.4 8.0 7.6 7.2 6.8 6.4 6.0 -50 -25 0 25 50 75 100 125 150
TA (C)
Supply Current versus Applied VCC
8.66 8.64 8.62 8.60 8.58 8.56 8.54 8.52 8.50 8.48 8.46 8.44 4.5 4.6 4.7 4.8 4.9 5 VCC (V) 5.1 5.2 5.3 5.4 5.5
ICC (mA)
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Output Voltage versus Primary Current VCC = 5 V
5.0 4.5 4.0 3.5
VOUT (V)
3.0 2.5 2.0 1.5 1.0 0.5 0 -20 -15 -10 -5 0 IP (A) 5 10 15 20
C -40 -20 25 85 150
Sensitivity versus Primary Current VCC = 5 V
110 108 106 104
C -40 -20 25 85 150
Sens (mV/A)
102 100 98 96 94 92 90
-20
-15
-10
-5
0 IP (A)
5
10
15
20
5
ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Zero Current Output Voltage vs. Ambient Temperature IP = 0 A
2.520 2.516 2.512
VOUT(Q) (V)
2.508 2.504 2.500 2.496 2.492 2.488 2.484 2.480 -50
-25
0
25
50
75
100
125
150
TA (C)
Zero Current Output Currrent versus Ambient Temperature
0.20 0.16 0.12
(Data in above chart converted to amperes) IP = 0 A
IVOUT(Q) (A)
0.08 0.04 0 -0.04 -0.08 -0.12 -0.16 -0.20 -50 -25 0 25 50 75 100 125 150
TA (C)
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Magnetic Offset versus Ambient Temperature
VCC = 5 V; IP = 0 A, after excursion to 20 A
1.0 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -50
VOM (A)
-25
0
25
50 TA (C)
75
100
125
150
Nonlinearity versus Ambient Temperature
VCC = 5 V IP = 15 A
2.0 1.8 1.6 1.4
ELIN (%)
1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 0 25 50 75 100 125 150
TA (C)
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Typical Percentage Error versus Ambient Temperature
Measurements at TA = -40, -20, 0, 25, 70, 85, 125, and 150 C 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -40 -20 0 Mean + 3 Sigma Mean Mean - 3 Sigma
ETOT (% of 15 A)
20
40
60
80
100
120
140
TA (C)
Attenuation of ACS704 Output versus AC Sinusoidal Current Frequency
dB Change from 5 kHz Response
0 -1.0 -2.0 -3.0 -4.0 -5.0 -6.0 -7.0 0 10 20 30 40 50 60 70
3A 5A 10 A
AC Current Frequency (kHz)
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Step Response of ACS704ELC-015 at TA=25C
ACS704 Output (mV)
15 A Excitation Signal
Typical Peak-to-Peak Noise of ACS704ELC-015 at TA=25C
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
ACS704ELC-015 Noise Filtering and Frequency Response Performance
Break Frequency of Filter on Output (kHz) Unfiltered 50 40 10 7.0 3.3 100 Nominal Programmed Sensitivity (mV/A) Measured Rise Time for 5 A Step, filtered (s) 9 10.5 12 35 70 101 Bandwidth as Derived from Step Response (kHz) 40 33.3 30 10 5 3.3
Peak-toPeak Noise (mV) 75 46 43 25 17 12
Resolution with Filtering (A) 0.75 0.46 0.43 0.25 0.17 0.12
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Definitions of Accuracy Characteristics
Sensitivity (Sens). The change in sensor output in response to a 1 A change through the primary conductor. The sensitivity is the product of the magnetic circuit sensitivity (G / A) and the linear IC amplifier gain (mV/G). The linear IC amplifier gain is programmed at the factory to optimize the sensitivity (mV/A) for the full-scale current of the device. Noise (VNOISE). The product of the linear IC amplifier gain (mV/G) and the noise floor for the Allegro Hall effect linear IC (1 G). The noise floor is derived from the thermal and shot noise observed in Hall elements. Dividing the noise (mV) by the sensitivity (mV/A) provides the smallest current that the device is able to resolve. Nonlinearity (ELIN). Linearity is the degree to which the voltage output from the sensor varies in direct proportion to the primary current through its full-scale amplitude. Conversely, nonlinearity reveals the maximum deviation from the ideal transfer curve for this transducer. Nonlinearity in the output can be attributed to the gain variation across temperature and saturation of the flux concentrator approaching the full-scale current. The following equation is used to derive the nonlinearity:
100 1-
{[
100
(Vout_full-scale amperes - VOUT(Q) ) 2 (Vout_half-scale amperes - VOUT(Q) )
[{
where Vout_full-scale amperes = the output voltage (V) when the sensed current approximates full-scale IP . Symmetry (ESYM). The degree to which the absolute voltage output from the sensor varies in proportion to either a positive or negative full-scale primary current. The following equation is used to derive symmetry:
Vout_+full-scale amperes - VOUT(Q) VOUT(Q) -Vout_-full-scale amperes
Quiescent output voltage (VOUT(Q)). The output of the sensor when the primary current is zero. For a unipolar supply voltage, it nominally remains at VCC 2. Thus, VCC = 5 V translates into VOUT(Q) = 2.5 V. Variation in VOUT(Q) can be attributed to the resolution of the Allegro linear IC quiescent voltage trim and thermal drift. Electrical offset voltage (VOE). The deviation of the device output from its ideal quiescent value of VCC / 2 due to nonmagnetic causes. To convert this voltage to amperes, divide by the device sensitivity, Sens. Accuracy (ETOT). The accuracy represents the maximum deviation of the actual output from its ideal value. This is also known as the total ouput error. The accuracy is illustrated graphically in the Output Voltage versus Current chart on the following page. Accuracy is divided into four areas: * 0 A at 25C. Accuracy of sensing zero current flow at 25C, without the effects of temperature. * 0 A over temperature. Accuracy of sensing zero current flow including temperature effects. * Full-scale current at 25C. Accuracy of sensing the full-scale current at 25C, without the effects of temperature. * Full-scale current over temperature. Accuracy of sensing full-scale current flow including temperature effects.
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Output voltage vs. current, illustrating sensor accuracy at 0 A and at full-scale current
Increasing VOUT (V)
Accuracy Over Temperature
Accuracy 25C Only Average VOUT Accuracy Over Temperature
Accuracy 25C Only
-IP (A)
-15 A
15 A
+IP (A)
Full Scale
0A
Accuracy 25C Only Accuracy Over Temperature
Decreasing VOUT (V)
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Definitions of Dynamic Response Characteristics
Propagation delay (tPROP): The time required for the sensor output to reflect a change in the primary current signal. Propagation delay is attributed to inductive loading within the linear IC package, as well as in the inductive loop formed by the primary conductor geometry. Propagation delay can be considered as a fixed time offset and may be compensated.
I (%) 90 Primary Current
Transducer Output 0 Propagation Time, tPROP t
Response time (tRESPONSE): The time interval between a) when the primary current signal reaches 90% of its final value, and b) when the sensor reaches 90% of its output corresponding to the applied current.
I (%) 90 Primary Current
Transducer Output 0 Response Time, tRESPONSE t
Rise time (tr): The time interval between a) when the sensor reaches 10% of its full scale value, and b) when it reaches 90% of its full scale value. The rise time to a step response is used to derive the bandwidth of the current sensor, in which (-3 dB) = 0.35 / tr. Both tr and tRESPONSE are detrimentally affected by eddy current losses observed in the conductive IC ground plane.
I (%) 90
Primary Current
Transducer Output 10 0 Rise Time, tr t
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Standards and Physical Specifications Parameter Flammability (package molding compound) Fire and Electric Shock Creepage distance, current terminals to sensor pins* Clearance distance, current terminals to sensor pins* Specification UL recognized to UL 94V-0
UL60950-1:2003 EN60950-1:2001 CAN/CSA C22.2 No. 60950-1:2003
3 mm 3 mm
*Limits determined by separation of solder pad lands for leads.
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Chopper Stabilization Technique
Chopper Stabilization is an innovative circuit technique that is used to minimize the offset voltage of a Hall element and an associated on-chip amplifier. Allegro patented a Chopper Stabilization technique that nearly eliminates Hall IC output drift induced by temperature or package stress effects. This offset reduction technique is based on a signal modulation-demodulation process. Modulation is used to separate the undesired dc offset signal from the magnetically induced signal in the frequency domain. Then, using a low-pass filter, the modulated dc offset is suppressed while the magnetically induced signal passes through the filter. As a result of this chopper stabilization approach, the output voltage from the Hall IC is desensitized to the effects of temperature and mechanical stress. This technique produces devices that have an extremely stable Electrical Offset Voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. This technique is made possible through the use of a BiCMOS process that allows the use of low-offset and low-noise amplifiers in combination with high-density logic integration and sample and hold circuits.
Regulator
Clock/Logic Hall Element Amp Low-Pass Filter
Concept of Chopper Stabilization Technique
Sample and Hold
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Applications Information
Transient Common-Mode Voltage Rejection in the ACS704 In order to quantify transient common-mode voltage rejection for the ACS704, a device was soldered onto a printed circuit board. A 0.1 F bypass capacitor and a 5 V dc power supply were connected between VCC and GND (pins 8 and 5) for this device. A 10 k load resistor and a 0.01 F capacitor were connected in parallel between the VOUT pin and the GND pin of the device (pins 7 and 5).
1 2 3
V1 VOUT=0V VOUT=20VPP freq=variable
8 7 I P 6 5 Output
C3 C=0.01F C0 C=0.1F
Vcc
V0 VDC=5V
4
R=10k R0
Ground
GND
ACS704 Schematic Diagram of the Circuit used to Measure Transient Rejection
A function generator was connected between the primary current conductor (pins 1 thru 4) and the GND pin of the device (pin 5). This function generator was configured to generate a 10 V peak (20 V peak-to-peak) sine wave between pins 1-4 and pin 5. Note that the sinusoidal stimulus was applied such that no electrical current would flow through the copper conductor composed of pins 1-4 of this device. The frequency of this sine wave was varied from 60 Hz to 5 MHz in discrete steps. At each frequency, the statistics feature of an oscilloscope was used to measure the voltage variations (noise) on the ACS704 output in mV (peak to peak). The noise was measured both before and after the application of the stimulus. Transient common-mode voltage rejection as a function of frequency is shown in the following figure.
-30 Transient Rejection (dB) -35 -40 -45 -50 -55 -60 0.06 1 10 100 300 600 800 1000 3000 5000
Frequency of 20 V Peak-to-Peak Stimulus (kHz) 16
ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
The Effect of PCB Layout on ACS704 Electrical Performance
Eight different PC boards were fabricated to characterize the effect of PCB design on the operating junction temperature of the Hall-effect IC inside of the ACS704. These PC boards are shown in the figure below.
2 oz. Cu on one side of board
2 oz. Cu on both sides of board
An ACS704 device was soldered onto each PC board before beginning the thermal testing. Thermal management tests were conducted with the following test conditions: Tests were conducted at ambient temperature, Ta = 20C. All tests were conducted in still air. 14 gauge wires were used to connect a power supply to a single PC board. These wires carry the 15 A dc primary current during the tests. A 15 A dc primary current was applied to a single PC board containing an ACS704 device. This current flowed from pins 1 and 2 to pins 3 and 4 of the ACS704 package. A 1 mA current was forced from the GND pin to the VCC pin by a Fluke 179 True RMS Multimeter. This was the only power applied to pins 5-8 of the ACS704 package during testing. The voltage required to force the 1 mA current from the GND pin to the VCC pin was measured after applying the 15 A primary current for approximately 25 minutes. A graph similar to the graph below was used to determine the junction temperature of the ACS704.
Voltage vs. Temperature Curve used to Determine Die Junction Temperature
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
The results of the testing are shown in the following table.
Effect of PCB Layout on ACS704 Thermal Performance
Tested at 15A, TA = 20C, still air, 2 oz. copper traces
PC Boards Sides with Traces Trace Width (mm) 4 1 1.5 4 1.5 4 2 1.5 4 1.5 Trace Length (mm) 50 50 10 10 50 50 10 10 Improved PC Board Designs The eight PC boards in the figure above do not represent an ideal PC board for use with the ACS704. The ACS704 evaluation boards, for sale at the Allegro Web site On-Line Store, represent a more optimal PC board design (see photo below). On the evaluation boards, the current to be sensed flows through very wide traces that were fabricated using 2 layers of 2 oz. copper. Thermal management tests were conducted on the Allegro evaluation boards and all tests were performed using the same test conditions described in the bulleted list above. The results for these thermal tests are shown in the table below. When using the Allegro evaluation boards we see that even at an applied current of 20 A the junction temperature of the ACS704 is only ~30 degrees above ambient temperature. Temperature Rise Above Ambient (C) 90 Overheated 48 110 53 106 38 54
ACS704 Thermal Performance on the Allegro Eval PC Boards
Applied Current (A) Ta = 20C, Still Air 15 20
Temp Rise Above Ambient (C) 22 31
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ACS704ELC-015
Package LC
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.
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ACS704ELC015-DS, Rev. 2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com

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