Preliminary Specification Allegro Current Sensor: ACS750 The Allegro Current Sensor provides an economical and precise solution for current sensing in automotive and industrial systems, packaged for easy implementation. Typical applications include motor control, load management, switched mode power supplies and over-current fault protection. The sensor consists of a precision linear Hall IC optimized to an internal magnetic circuit to increase device sensitivity. A combination of a precisely controlled self-aligning assembly process (patents pending) and the factory programmed precision of the linear Hall sensor result in high level performance and product uniformity. The power lead frame used for current sensing (pins 4 and 5) is designed for extremely low power loss. The power leads are also electrically isolated from the sensor leads (pins 1 – 3). This isolation allows the Allegro Current Sensor to be used in applications requiring electrical isolation without the use of opto-isolators or other isolating feedback techniques. Pin 1: Pin 2: Pin 3: Pin 4: Pin 5: An electrical current flowing from pins 4 to 5 will generate an analog voltage >Vcc/2 on the output. Vcc Gnd Output Ip-+ Ip- ABSOLUTE MAXIMUM RATINGS 1 Over-Current ………………………. . 225 A Supply Voltage, Vcc..........……….….. 16V Output Voltage .................……......... 16V Output Current Source....……..………3mA Output Current Sink ………..……… 10mA Operating Temperature .…...-40°C to 150°C Storage Temperature................…......170°C Maximum junction temperature...…....165°C 1 1 sec pulse, 10% duty cycle Last updated January 8, 2003 Features and Benefits • Monolithic Hall IC for High Reliability • ACS750LCA-075: +/- 75A up to 150°C • ACS750ECA-100: +/- 100A up to 85°C • Ultra-low Power Loss: Resistance = 120uΩ • No Trimming Required in the Application • Factory Trimmed for Gain and Offset • Linearity > 98.5% • Very Low Thermal Drift of Offset Voltage • 13kHz Bandwidth • Single supply +5V Operation • Ratiometric Output from Supply Voltage • On-chip transient protection Applications • Automotive Systems • Industrial Systems • Motor Control • Servo Systems • Power Conversion • Battery Monitor 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 1 Preliminary Specification Allegro Current Sensor: ACS750LCA Operating Characteristics Characteristic Symbol ELECTRICAL CHARACTERISTICS Test Conditions Limits Min. Typ. Max. Units -40°C to 150°C -75 75 Primary Sensed Current IP A -40°C to 85°C -100 100 Supply Voltage Vcc 4.5 5.0 5.5 V Supply Current Icc Vcc =5.0V, Output open 7 10 mA Output Resistance Rout Iout = 1.2 mA 1 2 Ω Isolation Voltage2 VISO Between pins 1-3 and 4-5 2.5 kV Propagation time tpropagation 4 IP = ±50A; T = +25°C µs Response time trespone 27 IP = ±50A; T = +25°C µs Rise time trise time 26 IP = ±50A; T = +25°C µs Frequency Bandwidth f -3dB 13 kHz PERFORMANCE CHARACTERISTICS (Over -40°C to 150°C temperature range unless otherwise specified) 18.75 19.75 20.75 IP = ±75A; T = +25°C Sensitivity Sens mV/A 18.5 19.5 20.5 IP = ±100A;T = +25°C Peak to peak; T = +25°C Noise3 10 mV BW = 40kHz 1.3 3.5 % IP = ±75A, T = -40°C to 150°C Non-linearity 2.4 5 % IP = ±100A, T = -40°C to 85°C 94 100 106 % IP = ±75A, T = -40°C to 150°C Symmetry Sym 94 100 106 % IP = ±100A, T = -40°C to 85°C 4 Quiescent Output Voltage VOQ IP = 0 A; T = +25°C -20 Vcc/2 +20 mV Thermal Drift of VOQ5 IP = 0 A -0.5 -0.12 +0.3 mV/°C ∆VOQ(T) -8 0 +7 IP = ±75A; T = -40°C to 150°C Thermal Drift of Sens % ∆Sens(T) IP = ±100A; T = -40°C to 85°C -9 0 +6 After excursion to +/-100A Magnetic Core Hysteresis6 VOH +/-0.3 +/-0.4 A T = +25°C T = +25°C +/-0.4 +/-1.8 A 0 Amp Accuracy 0A T = -40°C to 85°C +/-0.75 +/-2.7 A Including offset T = -40°C to 150°C +/-1.1 +/-3.2 A +/-1.0 +/-2.5 % IP = ±75A; T = +25°C +/-2.0 +/-4.0 % Full IP = ±100A; T = +25°C Scale 7 +/-2.4 +/-8.2 % IP = ±75A; T = -40°C to 150°C Total Accuracy +/-4.9 +/-12.6 % IP = ±100A; T = -40°C to 85°C 2 R.M.S. voltage for AC isolation test, 60 Hz, 5 min. duration. Refer to figure 5 for schematic of test circuit 4 Omitting magnetic hysteresis offset 5 Qvo & Sensitivity gain drift referenced to 25°C 6 Refer to figure 6 for hysteresis temperature characterization 7 Please contact Allegro sales representative for competitive comparison 3 Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 2 Preliminary Specification Allegro Current Sensor: ACS750LCA Definitions of accuracy characteristics Sensitivity: The sensitivity is the change in sensor output to 1A 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 trimmed to optimize the sensitivity (mV/A) for the full-scale current of the device. Variation in the sensitivity is affected by the resolution of the Allegro linear IC sensitivity trim (~10uV/step) and thermal drift (expressed in %/C). Noise: The noise is the product of the linear IC amplifier gain (mV/G) and the noise floor for the Allegro linear IC (~1Gauss). 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. Linearity: The 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. Linearity reveals the maximum deviation from the ideal transfer curve for this transducer. Non-linearity 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 linearity: [1-[(Vout_full-scale Amps –Vout_0A)/(2*(Vout_1/2 full-scale Amps –Vout_0A))]]*100 Symmetry: Symmetry is 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 Amps –Vout_0A)/(Vout_0A – Vout_-full-scale Amps)]*100 Quiescent output voltage: The quiescent output voltage (VOQ ) is the output of the sensor when the primary current is zero. For a unipolar supply voltage, VOQ nominally sits at Vcc/2. Vcc = 5V translates into VOQ = 2.5V. Variation in VOQ can be attributed to the resolution of the Allegro linear IC quiescent voltage trim (~2.5mV), magnetic hysteresis, and thermal drift (expressed in %/C). Magnetic hysteresis (offset): The magnetic offset is due to the residual magnetism (remanent field) that induces an offset in gauss. The magnetic offset error is highest when the magnetic circuit has been saturated, usually when the device has been subjected to a full scale or high current overload conditions. The magnetic offset is largely dependent on the material used as a flux concentrator. For most materials, the largest magnetic offset is observed at the lowest operating temperature. Accuracy: The accuracy represents the maximum deviation of the actual output from its ideal value. This is also known as the total error. The accuracy is illustrated graphically in Figure #1. The accuracy is divided into four areas of particular interest defined below: • • • • 0 A @ 25°C: Accuracy of sensing zero current flow at 25°C, without the effects of temperature. 0 A over temperature: Accuracy of sensing zero current flow including temperature effects. Full-scale current @ 25°C: Accuracy of sensing the full-scale current at 25°C, without the effects of temperature. Full-scale current over temperature: Accuracy of sensing full-scale current flow including temperature effects. Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 3 Preliminary Specification Allegro Current Sensor: ACS750LCA Figure 1: Output Voltage vs. Current, illustrating sensor accuracy at 0A and full-scale current Accuracy Full Scale 25°C Only Vout (Volts) Average Output Accuracy Full Scale Over Temp Accuracy 0Amp 25°C Only Accuracy 0Amp Over Temp I (Amps) +/-75A Full Scale Accuracy Full Scale 25°C Only Accuracy Full Scale Over Temp Figure 2: Block diagram of ACS750LCA-075 and linear Hall Effect IC functionality Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 4 Preliminary Specification Allegro Current Sensor: ACS750LCA Figure 3: Primary current versus typical output voltage across temperature Iprimary vs Vout, ACS750LCA-075 4.5 4 3.5 3 2.5 25C 85C 150C 2 1.5 1 0.5 -100 -80 -60 -40 -20 0 Amps 20 40 60 80 100 Figure 4: Primary current versus typical sensitivity across temperature Iprimary vs Sensitivity, ACS750LCA-075 22 20 mV/A 18 16 25C 85C 150C 14 12 10 10 20 30 Last updated January 8, 2003 40 50 Amps 60 70 80 90 100 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 5 Preliminary Specification Allegro Current Sensor: ACS750LCA Figure 5a – Test circuit used to determine peak to peak & RMS noise in linear IC output 43 Ohms 4” Coax Lead + 6V Battery 5.1V Zener 22uF .47nF DUT - Oscilloscope 24”Coax Lead Figure 5b. Noise Analysis of Linear Hall Effect IC within ACS750LCA-075 Package Peak to Peak Noise Frequency Spectrum of Noise Figure 5c: Peak to Peak Noise, Applying Low Pass Filter to the ACS750LCA-075 Output Low Pass Filter Break Frequency 1.4MHz 400kHz 160kHz 80kHz 40kHz Last updated January 8, 2003 Peak to Peak Noise 34mV 26mV 19mV 14mV 10mV 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 6 Preliminary Specification Allegro Current Sensor: ACS750LCA Figure 6: Peak to Peak Hysteresis Across Temperature (after excursion to +/-150A) mV Pk-Pk Hysteresis Temperature versus Typical Peak to Peak Hysteresis 20 18 16 14 12 10 8 6 4 2 0 -40 0 40 80 120 160 Temp (C) Figure 7: Peak Hysteresis versus Iprimary, 25C Typical Peak hysteresis versus Iprimary Pk hysteresis (Amps) 0.35 0.30 0.25 0.20 0.15 50 75 Last updated January 8, 2003 100 125 Amps 150 175 200 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 7 Preliminary Specification Allegro Current Sensor: ACS750LCA Figure 8: Rejection of Transient Voltage Signal on Iprimary, Typical Attenuation ~55dB Figure 9: Step response of ACS750LCA-075, Iprimary = 50A Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 8 Preliminary Specification Allegro Current Sensor: ACS750LCA Definitions of dynamic response characteristics Propagation delay: Propagation delay is the time that it takes for the sensor output to reflect a change in the primary current signal. Propagation delay is typically measured to be 3 to 5usec and is attributed to inductive loading within the linear IC package as well as the inductive loop formed by the primacy conductor geometry. Propagation delay can be considered as a fixed time offset and may be compensated. Response time: Response time is the time between when the primary current signal reaches 90% of its final value and when the sensor reaches 90% of its output corresponding to the applied current. Rise time: Rise time is the time between the sensor output reaching 10 and 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 ƒ(-3dB) = 0.35/tr. Both rise time and response time are detrimentally affected by eddy current losses observed in the conductive IC ground plane and to varying degrees, in the ferrous flux concentrator within the current sensor package. Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 9 Preliminary Specification Allegro Current Sensor: ACS750LCA Package thermal performance Symbol Electrical resistance of primary conductor Full-scale power dissipation Thermal resistance, Junction to Air Test Conditions Limits Rprimary IP = ±100A; +25°C Typical 130 Max. TBD Units µΩ Pprimary θJA IP = ±100A; +25°C T ambient = +25°C 1.5 9 TBD TBD W °C/W Figure 10: Thermal performance of current sensor, continuous current through primary conductor8 Self heating of 75A current sensor Primary current leads subjected to continuous overcurrent , Tambient ~25C 150 125 100A 240A 0A 100 75 50 25 0 0 2 4 6 8 10 12 14 16 18 20 time (minutes) Self heating of 75A current sensor Primary current leads subjected to continuous overcurrent , Tambient ~150C 400 350 100A 240A 0A 300 Temp C 250 200 150 100 50 0 0 2 4 6 8 10 12 14 16 18 20 22 24 time (minutes) 8 Over current peak operation is 225A peak, 1 second duration with 10% duty cycle Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 10 Preliminary Specification Allegro Current Sensor: ACS750LCA PACKAGE DRAWING Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 11 Preliminary Specification Allegro Current Sensor: ACS750LCA This page is intentionally left blank. Last updated January 8, 2003 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1993, 1995 Allegro MicroSystems, Inc. 12