ACS712_07

ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Features and Benefits ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ Low-noise analog signal path Device bandwidth is set via the new FILTER pin 5 μs output rise time in response to step input current 80 kHz bandwidth Total output error 1.5% at TA = 25°C Small footprint, low-profile SOIC8 package 1.2 mΩ internal conductor resistance 2.1 kVRMS minimum isolation voltage from pins 1-4 to pins 5-8 5.0 V, single supply operation 66 to 185 mV/A output sensitivity Output voltage proportional to AC or DC currents Factory-trimmed for accuracy Extremely stable output offset voltage Nearly zero magnetic hysteresis Ratiometric output from supply voltage TÜV America Certificate Number: U8V 06 05 54214 010 Description The Allegro® ACS712 provides economical and precise solutions for AC or DC current sensing in industrial, 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. The device consists of a precise, 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 after packaging. The output of the device has a positive slope (>VIOUT(Q)) 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 1.2 mΩ typical, providing low power Continued on the next page… Package: 8 Lead SOIC (suffix LC) Approximate Scale 1:1 Typical Application +5 V 1 2 IP 3 4 IP+ VCC 8 7 VOUT CBYP 0.1 μF IP+ VIOUT ACS712 IP– FILTER IP– GND 6 5 CF 1 nF Application 1. The ACS712 outputs an analog signal, VOUT . that varies linearly with the uni- or bi-directional AC or DC primary sensed current, IP , within the range specified. CF is recommended for noise management, with values that depend on the application. ACS712-DS, Rev. 6 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Description (continued) loss. The thickness of the copper conductor allows survival of the device at up to 5× overcurrent conditions. The terminals of the conductive path are electrically isolated from the sensor leads (pins 5 through 8). This allows the ACS712 current sensor to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. Selection Guide Part Number ACS712ELCTR-05B-T ACS712ELCTR-20A-T ACS712ELCTR-30A-T Packing* Tape and reel, 3000 pieces/reel Tape and reel, 3000 pieces/reel Tape and reel, 3000 pieces/reel The ACS712 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 device is Pb-free, except for flip-chip high-temperature Pb-based solder balls, currently exempt from RoHS. The device is fully calibrated prior to shipment from the factory. TA (°C) –40 to 85 –40 to 85 –40 to 85 Optimized Range, IP (A) ±5 ±20 ±30 Sensitivity, Sens (Typ) (mV/A) 185 100 66 *Contact Allegro for additional packing options. Absolute Maximum Ratings Characteristic Supply Voltage Reverse Supply Voltage Output Voltage Reverse Output Voltage Reinforced Isolation Voltage Symbol VCC VRCC VIOUT VRIOUT Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25°C VISO Voltage applied to leadframe (Ip+ pins), based on IEC 60950 Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25°C Basic Isolation Voltage Output Current Source Output Current Sink Overcurrent Transient Tolerance Nominal Operating Ambient Temperature Maximum Junction Temperature Storage Temperature VISO(bsc) IIOUT(Source) IIOUT(Sink) IP TA TJ(max) Tstg 1 pulse, 100 ms Range E Voltage applied to leadframe (Ip+ pins), based on IEC 60950 Notes Rating 8 –0.1 8 –0.1 2100 184 1500 354 3 10 100 –40 to 85 165 –65 to 170 Units V V V V V Vpeak V Vpeak mA mA A ºC ºC ºC Parameter Fire and Electric Shock Specification CAN/CSA-C22.2 No. 60950-1-03 UL 60950-1:2003 EN 60950-1:2001 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Functional Block Diagram +5 V VCC (Pin 8) Hall Current Drive IP+ (Pin 1) Sense Temperature Coefficient Trim Dynamic Offset Cancellation IP+ (Pin 2) Signal Recovery RF(INT) VIOUT (Pin 7) IP− (Pin 3) IP− (Pin 4) Sense Trim 0 Ampere Offset Adjust GND (Pin 5) FILTER (Pin 6) Pin-out Diagram IP+ IP+ IP– IP– 1 2 3 4 8 7 6 5 VCC VIOUT FILTER GND Terminal List Table Number 1 and 2 3 and 4 5 6 7 8 Name IP+ IP– GND FILTER VIOUT VCC Description Terminals for current being sensed; fused internally Terminals for current being sensed; fused internally Signal ground terminal Terminal for external capacitor that sets bandwidth Analog output signal Device power supply terminal Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor COMMON OPERATING CHARACTERISTICS1 over full range of TA , CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Supply Voltage Supply Current Output Capacitance Load Output Resistive Load Primary Conductor Resistance Rise Time Frequency Bandwidth Nonlinearity Symmetry Zero Current Output Voltage Power-On Time Magnetic Coupling2 Internal Filter Resistance3 1Device Symbol VCC ICC CLOAD RLOAD RPRIMARY tr f ELIN ESYM VIOUT(Q) tPO RF(INT) Test Conditions Min. 4.5 Typ. 5.0 10 – – 1.2 5 80 1.5 100 VCC × 0.5 35 12 1.7 Max. 5.5 13 10 – – – – – 102 – – – Units V mA nF kΩ mΩ μs kHz % % V μs G/A kΩ ELECTRICAL CHARACTERISTICS VCC = 5.0 V, output open VIOUT to GND VIOUT to GND TA = 25°C IP = IP(max), TA = 25°C, COUT = open –3 dB, TA = 25°C; IP is 10 A peak-to-peak Over full range of IP Over full range of IP Bidirectional; IP = 0 A, TA = 25°C Output reaches 90% of steady-state level, TJ = 25°C, 20 A present on leadframe – – 4.7 – – – – 98 – – – may be operated at higher primary current levels, IP, and ambient, TA , and internal leadframe temperatures, TA , provided that the Maximum Junction Temperature, TJ(max), is not exceeded. 21G = 0.1 mT. 3R F(INT) forms an RC circuit via the FILTER pin. COMMON THERMAL CHARACTERISTICS1 Min. Operating Internal Leadframe Temperature Junction-to-Lead Thermal Resistance2 Junction-to-Ambient Thermal Resistance 1Additional 2The Allegro Typ. – Max. 85 Value 5 23 Units °C Units °C/W °C/W TA RθJL RθJA E range Mounted on the Allegro ASEK 712 evaluation board –40 Mounted on the Allegro 85-0322 evaluation board, includes the power consumed by the board thermal information is available on the Allegro website. evaluation board has 1500 mm2 of 2 oz. copper on each side, connected to pins 1 and 2, and to pins 3 and 4, with thermal vias connecting the layers. Performance values include the power consumed by the PCB. Further details on the board are available from the Frequently Asked Questions document on our website. Further information about board design and thermal performance also can be found in the Applications Information section of this datasheet. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor x05B PERFORMANCE CHARACTERISTICS TA = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Sensitivity Noise Zero Current Output Slope Sensitivity Slope Total Output Error2 1Device Symbol IP Sens VNOISE(PP) ∆IOUT(Q) ∆Sens ETOT Test Conditions Over full range of IP, TA = 25°C Peak-to-peak, TA = 25°C, 185 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth TA = –40°C to 25°C TA = 25°C to 150°C TA = –40°C to 25°C TA = 25°C to 150°C IP =±5 A, TA = 25°C Min. –5 180 – – – – – – Typ. – 185 21 –0.26 –0.08 0.054 –0.008 ±1.5 Max. 5 190 – – – – – – Units A mV/A mV mV/°C mV/°C mV/A/°C mV/A/°C % may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature, TJ(max), is not exceeded. 2Percentage of I , with I = 5 A. Output filtered. P P x20A PERFORMANCE CHARACTERISTICS TA = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Sensitivity Noise Zero Current Output Slope Sensitivity Slope Total Output Error2 1Device Symbol IP Sens VNOISE(PP) ∆IOUT(Q) ∆Sens ETOT Test Conditions Over full range of IP, TA = 25°C Peak-to-peak, TA = 25°C, 100 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth TA = –40°C to 25°C TA = 25°C to 150°C TA = –40°C to 25°C TA = 25°C to 150°C IP =±20 A, TA = 25°C Min. –20 96 – – – – – – Typ. – 100 11 –0.34 –0.07 0.017 –0.004 ±1.5 Max. 20 104 – – – – – – Units A mV/A mV mV/°C mV/°C mV/A/°C mV/A/°C % may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature, TJ(max), is not exceeded. 2Percentage of I , with I = 20 A. Output filtered. P P x30A PERFORMANCE CHARACTERISTICS TA = –40°C to 85°C1, CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Sensitivity Noise Zero Current Output Slope Sensitivity Slope Total Output Error2 1Device Symbol IP Sens VNOISE(PP) ∆IOUT(Q) ∆Sens ETOT Test Conditions Over full range of IP , TA = 25°C Peak-to-peak, TA = 25°C, 66 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth TA = –40°C to 25°C TA = 25°C to 150°C TA = –40°C to 25°C TA = 25°C to 150°C IP = ±30 A , TA = 25°C Min. –30 64 – – – – – – Typ. – 66 7 –0.35 –0.08 0.007 –0.002 ±1.5 Max. 30 68 – – – – – – Units A mV/A mV mV/°C mV/°C mV/A/°C mV/A/°C % may be operated at higher primary current levels, IP, and ambient temperatures, TA, provided that the Maximum Junction Temperature, TJ(max), is not exceeded. 2Percentage of I , with I = 30 A. Output filtered. P P Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Characteristic Performance IP = 5 A, unless otherwise specified 10.9 10.8 10.7 ICC (mA) 10.6 10.5 10.4 10.3 10.2 10.1 -25 0 25 50 TA (°C) 75 100 125 150 10.0 4.5 4.6 4.7 4.8 4.9 5.0 5.1 VCC (V) 5.2 5.3 5.4 5.5 VCC = 5 V VCC = 5 V Mean Supply Current versus Ambient Temperature 10.30 10.25 10.20 10.15 10.10 10.05 10.00 9.95 9.90 9.85 9.80 9.75 -50 Supply Current versus Supply Voltage Mean ICC (mA) Magnetic Offset versus Ambient Temperature 0 –0.5 –1.0 IOM (mA) –2.0 –2.5 –3.0 –3.5 –4.0 –4.5 –5.0 -50 -25 0 25 50 TA (°C) 75 100 125 150 ELIN (%) –1.5 VCC = 5 V; IP = 0 A, After excursion to 20 A Nonlinearity versus Ambient Temperature 0.6 0.5 0.4 0.3 0.2 0.1 0 –50 VCC = 5 V –25 0 25 50 TA (°C) 75 100 125 150 Mean Total Output Error versus Ambient Temperature 8 6 4 ETOT (%) 2 0 –2 –4 –6 –8 –50 –25 0 25 50 TA (°C) 4.0 3.5 3.0 VIOUT (V) 2.5 2.0 1.5 1.0 0.5 0 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 TA (°C) –40 25 85 150 Sens (mV/A) VCC = 5 V 75 100 125 150 Sens (mV/A) Sensitivity versus Ambient Temperature 186.5 186.0 185.5 185.0 184.5 184.0 183.5 183.0 182.5 182.0 181.5 181.0 –50 –25 0 25 50 TA (°C) 75 100 125 150 Output Voltage versus Sensed Current 200.00 190.00 180.00 170.00 160.00 150.00 140.00 130.00 120.00 110.00 100.00 -6 Sensitivity versus Sensed Current TA (°C) –40 25 85 150 -4 -2 IP (A) 0 Ip (A) 2 4 6 0 A Output Voltage versus Ambient Temperature 2520 2515 VIOUT(Q) (mV) 2510 2505 2500 2495 2490 2485 -50 -25 0 25 50 TA (°C) 75 100 125 150 IP = 0 A 0 A Output Voltage Current versus Ambient Temperature 0.20 0.15 0.10 IOUT(Q) (A) 0.05 0 –0.05 –0.10 –0.15 -50 -25 0 25 50 TA (°C) 75 100 125 150 IP = 0 A Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Characteristic Performance IP = 20 A, unless otherwise specified 10.4 10.2 ICC (mA) 10.0 9.8 9.6 9.4 9.2 9.0 4.5 4.6 4.7 4.8 4.9 5.0 5.1 VCC (V) 5.2 5.3 5.4 5.5 VCC = 5 V Mean Supply Current versus Ambient Temperature 9.7 9.6 Mean ICC (mA) 9.5 9.4 9.3 9.2 9.1 -50 VCC = 5 V Supply Current versus Supply Voltage -25 0 25 50 TA (°C) 75 100 125 150 Magnetic Offset versus Ambient Temperature 0 –0.5 –1.0 IOM (mA) –2.0 –2.5 –3.0 –3.5 –4.0 –4.5 –5.0 -50 -25 0 25 50 TA (°C) 75 100 125 150 VCC = 5 V; IP = 0 A, After excursion to 20 A ELIN (%) –1.5 Nonlinearity versus Ambient Temperature 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 –50 –25 0 25 50 TA (°C) 75 100 125 150 Mean Total Output Error versus Ambient Temperature 8 6 4 ETOT (%) 2 0 –2 –4 –6 –8 –50 –25 0 25 50 TA (°C) 75 100 125 150 Sens (mV/A) 100.8 100.6 100.4 100.2 100.0 99.8 99.6 99.4 99.2 Sensitivity versus Ambient Temperature 99.0 –50 –25 0 25 50 TA (°C) 75 100 125 150 Output Voltage versus Sensed Current 5.0 4.5 VIOUT (V) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –25 –20 –15 –10 –5 0 IP (A) 5 10 TA (°C) –40 –20 25 85 125 15 20 25 VCC = 5 V Sens (mV/A) 4.0 110.00 108.00 106.00 104.00 102.00 100.00 98.00 96.00 94.00 92.00 Sensitivity versus Sensed Current TA (°C) –40 25 85 150 90.00 –25 –20 –15 –10 –5 5 0 Ip (A) 10 15 20 25 0 A Output Voltage versus Ambient Temperature 2525 2520 2515 VIOUT(Q) (mV) 0 A Output Voltage Current versus Ambient Temperature 0.25 0.20 0.15 IOUT(Q) (A) 2510 2505 2500 2495 2490 2485 -50 -25 0 25 IP = 0 A 0.10 0.05 0 –0.05 –0.10 IP = 0 A 50 TA (°C) 75 100 125 150 –0.15 -50 -25 0 25 50 TA (°C) 75 100 125 150 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Characteristic Performance IP = 30 A, unless otherwise specified 10.2 10.0 ICC (mA) 9.8 9.6 9.4 9.2 9.0 4.5 VCC = 5 V Mean Supply Current versus Ambient Temperature 9.6 9.5 9.4 Mean ICC (mA) 9.3 9.2 9.1 9.0 8.9 -50 VCC = 5 V Supply Current versus Supply Voltage -25 0 25 50 TA (°C) 75 100 125 150 4.6 4.7 4.8 4.9 5.0 5.1 VCC (V) 5.2 5.3 5.4 5.5 Magnetic Offset versus Ambient Temperature 0 –0.5 –1.0 IOM (mA) –2.0 –2.5 –3.0 –3.5 –4.0 –4.5 –5.0 -50 -25 0 25 50 TA (°C) 75 100 125 150 VCC = 5 V; IP = 0 A, After excursion to 20 A ELIN (%) –1.5 Nonlinearity versus Ambient Temperature 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 –50 –25 0 25 50 TA (°C) 75 100 125 150 VCC = 5 V Mean Total Output Error versus Ambient Temperature 8 6 4 ETOT (%) 2 0 –2 –4 –6 –8 –50 –25 0 25 50 TA (°C) 75 100 125 150 Sens (mV/A) 66.6 66.5 66.4 66.3 66.2 66.1 66.0 65.9 65.8 Sensitivity versus Ambient Temperature 65.7 –50 –25 0 25 50 TA (°C) 75 100 125 150 Output Voltage versus Sensed Current 5.0 4.5 VIOUT (V) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –30 –20 –10 0 IP (A) 10 TA (°C) –40 –20 25 85 125 20 30 VCC = 5 V Sens (mV/A) 4.0 70.00 69.00 68.00 67.00 66.00 65.00 64.00 63.00 62.00 61.00 Sensitivity versus Sensed Current TA (°C) –40 25 85 150 –20 –10 0 Ip (A) 10 20 30 60.00 –30 0 A Output Voltage versus Ambient Temperature 2535 2530 2525 VIOUT(Q) (mV) 2520 2515 2510 2505 2500 2495 2490 2485 -50 -25 0 25 50 TA (°C) 75 100 125 150 0 A Output Voltage Current versus Ambient Temperature 0.35 0.30 0.25 0.20 IOUT(Q) (A) IP = 0 A 0.15 0.10 0.05 0 –0.05 –0.10 –0.15 -50 -25 0 25 IP = 0 A 50 TA (°C) 75 100 125 150 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor 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. Linearity (ELIN). The degree to which the voltage output from the sensor varies in direct proportion to the primary current through its full-scale amplitude. Nonlinearity in the output can be attributed to the saturation of the flux concentrator approaching the full-scale current. The following equation is used to derive the linearity: 100 1– Accuracy is divided into four areas: • 0 A at 25°C. Accuracy of sensing zero current flow at 25°C, without the effects of temperature. • 0 A over Δ temperature. Accuracy of sensing zero current flow including temperature effects. • Full-scale current at 25°C. Accuracy of sensing the full-scale current at 25°C, without the effects of temperature. • Full-scale current over Δ temperature. Accuracy of sensing fullscale current flow including temperature effects. Ratiometry. The ratiometric feature means that its 0 A output, VIOUT(Q), (nominally equal to VCC/2) and sensitivity, Sens, are proportional to its supply voltage, VCC . The following formula is used to derive the ratiometric change in 0 A output voltage, ΔVIOUT(Q)RAT (%). 100 VIOUT(Q)VCC / VIOUT(Q)5V {[ Δ gain × % sat ( VIOUT_full-scale amperes – VIOUT(Q) ) 2 (VIOUT_half-scale amperes – VIOUT(Q) ) [{  VCC / 5 V  The ratiometric change in sensitivity, ΔSensRAT (%), is defined as: 100 SensVCC / Sens5V where VIOUT_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 formula is used to derive symmetry: 100 VIOUT_+ full-scale amperes – VIOUT(Q) ‰ VCC / 5 V  Output Voltage versus Sensed Current Accuracy at 0 A and at Full-Scale Current Increasing VIOUT(V) Accuracy Over Temp erature Accuracy 25°C Only Average VIOUT Accuracy Over Temp erature  VIOUT(Q) – VIOUT_–full-scale amperes  Quiescent output voltage (VIOUT(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 VIOUT(Q) = 2.5 V. Variation in VIOUT(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 at right. –IP (A) Accuracy 25°C Only IP(min) +IP (A) Full Scale IP(max) 0A Accuracy 25°C Only Accuracy Over Temp erature Decreasing VIOUT(V) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Definitions of Dynamic Response Characteristics Power-On Time (tPO). When the supply is ramped to its operating voltage, the device requires a finite time to power its internal components before responding to an input magnetic field. Power-On Time, tPO , is defined as the time it takes for the output voltage to settle within ±10% of its steady state value under an applied magnetic field, after the power supply has reached its minimum specified operating voltage, VCC(min), as shown in the chart at right. 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 ƒ(–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 200 180 160 140 120 100 80 60 40 20 0 0 Power on Time versus External Filter Capacitance IP =5 A IP =0 A Step Response TA=25°C tPO (μs) 10 20 CF (nF) 30 40 50 Output (mV) 15 A Excitation Signal Noise vs. Filter Cap 10000 1000 Noise(p-p) (mA) Noise versus External Filter Capacitance 100 10 1 0.01 0.1 1 CF (nF) 10 100 1000 Rise Time versus External Filter Capacitance 400 350 300 250 200 150 100 50 0 0 Rise Time versus External Filter Capacitance 1200 1000 tr(μs) 800 600 400 200 0 0 100 CF (nF) 0 1 4.7 10 22 47 100 220 470 500 tr (μs) 6.6 7.7 17.4 32.1 68.2 88.2 291.3 623.0 1120.0 } Expanded in chart at right 200 CF (nF) 300 400 tr(μs) 25 50 75 CF (nF) 100 125 150 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor 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 Sample and Hold Low-Pass Filter Concept of Chopper Stabilization Technique Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Typical Applications +5 V +5 V VPEAK C2 0.1 μF R4 10 kΩ CBYP 0.1 μF VRESET Q1 2N7002 1 IP+ VCC 8 7 RF 1 kΩ 6 5 CF 0.01 μF R1 100 kΩ CBYP 0.1 μF IP+ IP 3 4 ACS712 IP– FILTER IP– GND 6 5 R1 1 MΩ CF 1 nF R2 33 kΩ Application 2. Peak Detecting Circuit +5 V CBYP 0.1 μF CBYP 0.1 μF 1 2 IP 3 4 IP+ VCC 8 7 VOUT RF 2 kΩ 6 5 R1 10 kΩ CF 1 nF IP+ VIOUT ACS712 IP– FILTER IP– GND Application 4. Rectified Output. 3.3 V scaling and rectification application for A-to-D converters. Replaces current transformer solutions with simpler ACS circuit. C1 is a function of the load resistance and filtering desired. R1 can be omitted if the full range is desired. – RF 10 kΩ 2 D1 U1 LT1178 1N914 IP 3 4 R3 330 kΩ C1 0.1 μF IP+ VIOUT ACS712 IP– FILTER IP– GND Application 3. This configuration increases gain to 610 mV/A (tested using the ACS712ELC-05A). +5 V R1 33 kΩ RPU 100 kΩ D1 1N4448W 1 A-to-D Converter IP 2 IP+ VCC 8 7 R2 100 kΩ VOUT 4 3 IP+ VIOUT ACS712 C1 3 4 IP– FILTER IP– GND 6 5 CF 1 nF Application 5. 10 A Overcurrent Fault Latch. Fault threshold set by R1 and R2. This circuit latches an overcurrent fault and holds it until the 5 V rail is powered down. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com – IP+ VIOUT + 2 7 3 + 1 VCC 8 COUT 0.1 μF VOUT R2 100 kΩ 1 5 2 LM321 4 VOUT R3 3.3 kΩ C1 1000 pF – + 5 1 Fault 2 U1 LMV7235 D1 1N914 12 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor Improving Sensing System Accuracy Using the FILTER Pin In low-frequency sensing applications, it is often advantageous to add a simple RC filter to the output of the sensor. Such a lowpass filter improves the signal-to-noise ratio, and therefore the resolution, of the sensor output signal. However, the addition of an RC filter to the output of a sensor IC can result in undesirable sensor output attenuation — even for dc signals. Signal attenuation, ∆VATT , is a result of the resistive divider effect between the resistance of the external filter, RF (see Application 6), and the input impedance and resistance of the customer interface circuit, RINTFC. The transfer function of this resistive divider is given by: ∆VATT = VIOUT ⎜ ⎜ temperature. Therefore, signal attenuation will vary as a function of temperature. Note that, in many cases, the input impedance, RINTFC , of a typical analog-to-digital converter (ADC) can be as low as 10 kΩ. The ACS712 contains an internal resistor, a FILTER pin connection to the printed circuit board, and an internal buffer amplifier. With this circuit architecture, users can implement a simple RC filter via the addition of a capacitor, CF (see Application 7) from the FILTER pin to ground. The buffer amplifier inside of the ACS712 (located after the internal resistor and FILTER pin connection) eliminates the attenuation caused by the resistive divider effect described in the equation for ∆VATT. Therefore, the ACS712 device is ideal for use in high-accuracy applications that cannot afford the signal attenuation associated with the use of an external RC low-pass filter. VCC Pin 8 ⎛ ⎝ RINTFC RF + RINTFC ⎞ ⎟ ⎠ . Even if RF and RINTFC are designed to match, the two individual resistance values will most likely drift by different amounts over +5 V Pin 3 Pin 4 IP– IP– Allegro ACS706 Dynamic Offset Cancellation Application 6. When a low pass filter is constructed externally to a standard Hall effect device, a resistive divider may exist between the filter resistor, RF, and the resistance of the customer interface circuit, RINTFC. This resistive divider will cause excessive attenuation, as given by the transfer function for ∆VATT. Voltage Regulator To all subcircuits VIOUT Pin 7 Resistive Divider Input Filter 0.1 F Amp Out N.C. Pin 6 RF Application Interface Circuit Low Pass Filter Gain Temperature Coefficient Trim Control Offset CF 1 nF RINTFC IP+ IP+ Pin 1 Pin 2 GND Pin 5 +5 V VCC Pin 8 Dynamic Offset Cancellation Application 7. Using the FILTER pin provided on the ACS712 eliminates the attenuation effects of the resistor divider between RF and RINTFC, shown in Application 6. Allegro ACS712 Hall Current Drive IP+ Pin 1 IP+ Pin 2 Sense Temperature Coefficient Trim Buffer Amplifier and Resistor Signal Recovery VIOUT Pin 7 Input IP– Pin 3 IP– Pin 4 Sense Trim 0 Ampere Offset Adjust Application Interface Circuit RINTFC GND Pin 5 FILTER Pin 6 CF 1 nF Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 ACS712 Package LC, 8-pin SOIC Fully Integrated, Hall Effect-Based Linear Current Sensor with 2.1 kVRMS Voltage Isolation and a Low-Resistance Current Conductor 4.90 8 4º 0.21 3.90 A 6.00 0.84 1 2 0.25 SEATING PLANE GAUGE PLANE All dimensions nominal, not for tooling use (reference JEDEC MS-012 AA) Dimensions in millimeters A Terminal #1 mark area 8X 0.10 C 0.41 1.27 0.18 SEATING PLANE 1.75 MAX C Package Branding 1 2 3 4 8 7 6 5 Text 1 Text 2 Text 3 Two alternative patterns are used ACS712T RLCPPP YYWWA ACS 712 T R LC PPP YY WW A Allegro Current Sensor Device family number Indicator of 100% matte tin leadframe plating Operating ambient temperature range code Package type designator Primary sensed current Date code: Calendar year (last two digits) Date code: Calendar week Date code: Shift code ACS712T RLCPPP L...L YYWW ACS 712 T R LC PPP L...L YY WW Allegro Current Sensor Device family number Indicator of 100% matte tin leadframe plating Operating ambient temperature range code Package type designator Primary sensed current Lot code Date code: Calendar year (last two digits) Date code: Calendar week Copyright ©2006, 2007, Allegro MicroSystems, Inc. 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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. 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. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14