ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor Features and Benefits Description The Allegro(R) 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, switchmode power supplies, and overcurrent fault protection. The device is not intended for automotive applications. Low-noise analog signal path Device bandwidth is set via the new FILTER pin 5 s output rise time in response to step input current 80 kHz bandwidth Total output error 1.5% at TA = 25C Small footprint, low-profile SOIC8 package 1.2 m 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 The device consists of a precise, low-offset, linear Hall 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 the Hall IC converts 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. TUV America Certificate Number: U8V 06 05 54214 010 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 sampling. The internal resistance of this conductive path is 1.2 m typical, providing low power loss. The thickness of the copper conductor allows survival of Package: 8 Lead SOIC (suffix LC) Continued on the next page... Approximate Scale 1:1 Typical Application 1 2 IP IP+ VCC IP+ VIOUT ACS712 3 4 IP- FILTER IP- GND +5 V 8 7 VOUT CBYP 0.1 F 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 sampled current, IP , within the range specified. CF is recommended for noise management, with values that depend on the application. ACS712-DS, Rev. 14 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Description (continued) the device at up to 5x overcurrent conditions. The terminals of the conductive path are electrically isolated from the signal leads (pins 5 through 8). This allows the ACS712 to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. 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. Selection Guide Part Number Packing* TA (C) Optimized Range, IP (A) Sensitivity, Sens (Typ) (mV/A) ACS712ELCTR-05B-T Tape and reel, 3000 pieces/reel -40 to 85 5 185 ACS712ELCTR-20A-T Tape and reel, 3000 pieces/reel -40 to 85 20 100 ACS712ELCTR-30A-T Tape and reel, 3000 pieces/reel -40 to 85 30 66 *Contact Allegro for additional packing options. Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Supply Voltage VCC 8 V Reverse Supply Voltage VRCC -0.1 V Output Voltage VIOUT 8 V Reverse Output Voltage VRIOUT -0.1 V Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25C 2100 VAC VISO Maximum working voltage according to UL60950-1 184 Vpeak Pins 1-4 and 5-8; 60 Hz, 1 minute, TA=25C 1500 VAC Basic Isolation Voltage VISO(bsc) Maximum working voltage according to UL60950-1 354 Vpeak Output Current Source IIOUT(Source) 3 mA Reinforced Isolation Voltage Output Current Sink IIOUT(Sink) Overcurrent Transient Tolerance Nominal Operating Ambient Temperature Maximum Junction Temperature Storage Temperature IP 1 pulse, 100 ms TA Range E 10 mA 100 A -40 to 85 C TJ(max) 165 C Tstg -65 to 170 C Parameter Specification Fire and Electric Shock 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Functional Block Diagram +5 V VCC (Pin 8) Hall Current Drive IP+ (Pin 1) Sense Temperature Coefficient Trim Dynamic Offset Cancellation IP+ (Pin 2) IP- (Pin 3) Signal Recovery VIOUT (Pin 7) RF(INT) Sense Trim IP- (Pin 4) 0 Ampere Offset Adjust GND (Pin 5) FILTER (Pin 6) Pin-out Diagram IP+ 1 8 VCC IP+ 2 7 VIOUT IP- 3 6 FILTER IP- 4 5 GND Terminal List Table Number Name 1 and 2 IP+ Terminals for current being sampled; fused internally Description 3 and 4 IP- Terminals for current being sampled; fused internally 5 GND 6 FILTER 7 VIOUT 8 VCC 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 COMMON OPERATING CHARACTERISTICS1 over full range of TA , CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units 4.5 5.0 5.5 V - 10 13 mA ELECTRICAL CHARACTERISTICS Supply Voltage VCC Supply Current ICC VCC = 5.0 V, output open Output Capacitance Load CLOAD VIOUT to GND - - 10 nF Output Resistive Load RLOAD VIOUT to GND 4.7 - - k - 1.2 - m Primary Conductor Resistance RPRIMARY TA = 25C Rise Time tr IP = IP(max), TA = 25C, COUT = open - 5 - s Frequency Bandwidth f -3 dB, TA = 25C; IP is 10 A peak-to-peak - 80 - kHz Nonlinearity ELIN Over full range of IP - 1.5 - % Symmetry ESYM Over full range of IP 98 100 102 % Bidirectional; IP = 0 A, TA = 25C - VCC x 0.5 - V Output reaches 90% of steady-state level, TJ = 25C, 20 A present on leadframe - 35 - s 12 - G/A Zero Current Output Voltage Power-On Time VIOUT(Q) tPO Magnetic Coupling2 Internal Filter Resistance3 - RF(INT) 1.7 k 1Device 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 Operating Internal Leadframe Temperature TA E range Min. Typ. Max. -40 - 85 Units C Value Units Junction-to-Lead Thermal Resistance2 RJL Mounted on the Allegro ASEK 712 evaluation board 5 C/W Junction-to-Ambient Thermal Resistance RJA Mounted on the Allegro 85-0322 evaluation board, includes the power consumed by the board 23 C/W 1Additional 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. 2The Allegro Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 x05B PERFORMANCE CHARACTERISTICS1 TA = -40C to 85C, CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Sensitivity Noise Symbol Sens VNOISE(PP) Zero Current Output Slope Sensitivity Slope Total Output Error2 Test Conditions Min. Typ. Max. -5 - 5 A 180 185 190 mV/A Peak-to-peak, TA = 25C, 185 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth - 21 - mV mV/C IP IOUT(Q) Sens ETOT Over full range of IP, TA = 25C Units TA = -40C to 25C - -0.26 - TA = 25C to 150C - -0.08 - mV/C TA = -40C to 25C - 0.054 - mV/A/C TA = 25C to 150C - -0.008 - mV/A/C IP =5 A, TA = 25C - 1.5 - % 1Device 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 CHARACTERISTICS1 TA = -40C to 85C, CF = 1 nF, and VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Sensitivity Noise Symbol Sens VNOISE(PP) Zero Current Output Slope Sensitivity Slope Total Output Error2 Test Conditions Min. Typ. Max. -20 - 20 A Over full range of IP, TA = 25C 96 100 104 mV/A Peak-to-peak, TA = 25C, 100 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth - 11 - mV mV/C IP IOUT(Q) Sens ETOT Units TA = -40C to 25C - -0.34 - TA = 25C to 150C - -0.07 - mV/C TA = -40C to 25C - 0.017 - mV/A/C TA = 25C to 150C - -0.004 - mV/A/C IP =20 A, TA = 25C - 1.5 - % 1Device 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 CHARACTERISTICS1 TA = -40C to 85C, 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 Symbol Test Conditions Min. Typ. Max. -30 - 30 A Over full range of IP , TA = 25C 63 66 69 mV/A Peak-to-peak, TA = 25C, 66 mV/A programmed Sensitivity, CF = 47 nF, COUT = open, 2 kHz bandwidth - 7 - mV mV/C IP Sens VNOISE(PP) IOUT(Q) Sens ETOT Units TA = -40C to 25C - -0.35 - TA = 25C to 150C - -0.08 - mV/C TA = -40C to 25C - 0.007 - mV/A/C TA = 25C to 150C - -0.002 - mV/A/C IP = 30 A , TA = 25C - 1.5 - % 1Device 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Characteristic Performance IP = 5 A, unless otherwise specified 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 10.9 10.8 10.7 ICC (mA) Mean ICC (mA) Mean Supply Current versus Ambient Temperature VCC = 5 V 10.6 VCC = 5 V 10.5 10.4 10.3 10.2 10.1 -25 0 25 50 75 100 125 10.0 4.5 150 4.7 4.6 4.8 4.9 TA (C) Magnetic Offset versus Ambient Temperature -2.0 ELIN (%) IOM (mA) -1.5 VCC = 5 V; IP = 0 A, After excursion to 20 A -2.5 -3.0 VCC = 5 V 0.4 0.3 0.2 -3.5 -4.0 0.1 -4.5 -5.0 -50 -25 0 25 50 75 100 125 0 -50 150 -25 0 25 TA (C) 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 Sens (mV/A) 6 4 2 0 -2 -4 -6 -25 0 25 75 50 100 125 150 -25 0 25 TA (C) 125 150 75 50 100 125 150 TA (C) Output Voltage versus Sensed Current 200.00 Sensitivity versus Sensed Current 190.00 3.5 Sens (mV/A) VCC = 5 V 3.0 2.5 TA (C) -40 25 85 150 2.0 1.5 1.0 180.00 170.00 160.00 TA (C) -40 25 85 150 150.00 140.00 130.00 120.00 0.5 110.00 0 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 100.00 -6 -4 -2 IP (A) 0 A Output Voltage versus Ambient Temperature 0 Ip (A) 2 4 6 0 A Output Voltage Current versus Ambient Temperature 2520 0.20 2515 0.15 IP = 0 A 2505 2500 0.05 0 2495 -0.05 2490 -0.10 -25 0 25 50 TA (C) 75 IP = 0 A 0.10 IOUT(Q) (A) 2510 2485 -50 100 Sensitivity versus Ambient Temperature 8 -8 -50 75 50 TA (C) Mean Total Output Error versus Ambient Temperature ETOT (%) 5.5 0.5 -1.0 VIOUT (V) 5.4 5.3 0.6 -0.5 VIOUT(Q) (mV) 5.2 Nonlinearity versus Ambient Temperature 0 4.0 5.0 5.1 VCC (V) 100 125 150 -0.15 -50 -25 0 25 50 75 100 125 150 TA (C) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Characteristic Performance IP = 20 A, unless otherwise specified Supply Current versus Supply Voltage 9.7 10.4 9.6 10.2 9.5 ICC (mA) Mean ICC (mA) Mean Supply Current versus Ambient Temperature VCC = 5 V 9.4 9.3 VCC = 5 V 10.0 9.8 9.6 9.4 9.2 9.2 9.1 -50 -25 0 25 50 75 100 125 9.0 4.5 150 4.6 4.7 4.8 4.9 TA (C) Magnetic Offset versus Ambient Temperature ELIN (%) -1.5 IOM (mA) 5.4 5.5 0.30 -1.0 -2.0 -2.5 VCC = 5 V; IP = 0 A, After excursion to 20 A -3.0 -3.5 0.25 0.20 0.15 0.10 -4.0 0.05 -4.5 -5.0 -50 -25 0 25 50 75 100 125 0 -50 150 -25 0 25 Mean Total Output Error versus Ambient Temperature 6 100.6 4 100.4 Sens (mV/A) 100.8 2 0 -2 99.8 99.6 99.4 99.2 25 75 50 100 125 99.0 -50 150 -25 0 25 TA (C) Output Voltage versus Sensed Current 110.00 4.5 108.00 4.0 106.00 Sens (mV/A) VCC = 5 V 3.0 TA (C) -40 -20 25 85 125 2.5 2.0 1.5 1.0 0.5 0 -25 -20 -15 -10 -5 0 5 100 125 150 10 15 Sensitivity versus Sensed Current TA (C) -40 25 85 150 104.00 102.00 100.00 98.00 96.00 94.00 92.00 20 90.00 -25 -20 -15 -10 25 -5 IP (A) 0 A Output Voltage versus Ambient Temperature 5 0 Ip (A) 10 15 20 25 0 A Output Voltage Current versus Ambient Temperature 2525 0.25 2520 0.20 2515 0.15 2510 IOUT(Q) (A) IP = 0 A 2505 2500 0.05 0 -0.05 2490 -0.10 -25 0 25 50 TA (C) 75 100 125 150 IP = 0 A 0.10 2495 2485 -50 75 50 TA (C) 5.0 3.5 150 100.0 -6 0 125 100.2 -4 -25 100 Sensitivity versus Ambient Temperature 8 -8 -50 75 50 TA (C) TA (C) ETOT (%) 5.3 Nonlinearity versus Ambient Temperature -0.5 VIOUT (V) 5.2 0.35 0 VIOUT(Q) (mV) 5.0 5.1 VCC (V) -0.15 -50 -25 0 25 50 75 100 125 150 TA (C) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Characteristic Performance IP = 30 A, unless otherwise specified Mean Supply Current versus Ambient Temperature Supply Current versus Supply Voltage 9.6 10.2 9.5 10.0 ICC (mA) Mean ICC (mA) 9.4 VCC = 5 V 9.3 9.2 9.8 VCC = 5 V 9.6 9.4 9.1 9.2 9.0 8.9 -50 -25 0 25 50 75 100 125 9.0 4.5 150 4.7 4.6 4.9 4.8 TA (C) 0.45 -0.5 0.40 -1.0 0.35 -1.5 0.30 ELIN (%) IOM (mA) 0 -2.0 VCC = 5 V; IP = 0 A, After excursion to 20 A -3.0 0.10 0.05 25 50 VCC = 5 V 0.20 -4.5 0 75 100 125 0 -50 150 -25 0 25 100 125 150 Sensitivity versus Ambient Temperature 8 66.6 6 66.5 4 66.4 Sens (mV/A) ETOT (%) Mean Total Output Error versus Ambient Temperature 2 0 66.3 66.2 66.1 -2 66.0 -4 65.9 -6 65.8 -8 -50 -25 0 25 75 50 100 125 65.7 -50 150 -25 0 25 TA (C) 70.00 4.5 69.00 VCC = 5 V 3.0 TA (C) -40 -20 25 85 125 2.5 2.0 1.5 1.0 0.5 -20 -10 0 150 20 10 67.00 66.00 65.00 TA (C) -40 25 85 150 64.00 63.00 62.00 61.00 60.00 -30 30 -20 -10 IP (A) 0 A Output Voltage versus Ambient Temperature 0 Ip (A) 20 10 30 0 A Output Voltage Current versus Ambient Temperature 2535 0.35 2530 0.30 2525 0.25 2520 0.20 IOUT(Q) (A) IP = 0 A 2515 2510 2505 0.10 0.05 0 2495 -0.05 2490 -0.10 -25 0 25 50 TA (C) 75 100 125 150 IP = 0 A 0.15 2500 2485 -50 125 68.00 Sens (mV/A) 4.0 0 -30 100 Sensitivity versus Sensed Current 5.0 3.5 75 50 TA (C) Output Voltage versus Sensed Current VIOUT (V) 75 50 TA (C) TA (C) VIOUT(Q) (mV) 5.5 0.25 -4.0 -25 5.4 5.3 0.15 -3.5 -5.0 -50 5.2 Nonlinearity versus Ambient Temperature Magnetic Offset versus Ambient Temperature -2.5 5.0 5.1 VCC (V) -0.15 -50 -25 0 25 50 75 100 125 150 TA (C) 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 IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor Definitions of Accuracy Characteristics Sensitivity (Sens). The change in device 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 IC 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- gain x % sat ( VIOUT_full-scale amperes - VIOUT(Q) ) 2 (VIOUT_half-scale amperes - VIOUT(Q) ) [{ Accuracy is divided into four areas: 0 A at 25C. Accuracy at the zero current flow at 25C, without the effects of temperature. 0 A over temperature. Accuracy at the zero current flow including temperature effects. Full-scale current at 25C. Accuracy at the the full-scale current at 25C, without the effects of temperature. Full-scale current over temperature. Accuracy at the 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, VIOUT(Q)RAT (%). 100 VCC / 5 V The ratiometric change in sensitivity, SensRAT (%), is defined as: where VIOUT_full-scale amperes = the output voltage (V) when the sampled current approximates full-scale IP . 100 Symmetry (ESYM). The degree to which the absolute voltage output from the IC varies in proportion to either a positive or negative full-scale primary current. The following formula is used to derive symmetry: 100 VIOUT(Q)VCC / VIOUT(Q)5V SensVCC / Sens5V VCC / 5 V Output Voltage versus Sampled Current Accuracy at 0 A and at Full-Scale Current Increasing VIOUT(V) Accuracy Over $Temp erature VIOUT_+ full-scale amperes - VIOUT(Q) VIOUT(Q) - VIOUT_-full-scale amperes Accuracy 25C Only Quiescent output voltage (VIOUT(Q)). The output of the device 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 output error. The accuracy is illustrated graphically in the output voltage versus current chart at right. Average VIOUT Accuracy Over $Temp erature Accuracy 25C Only IP(min) -IP (A) +IP (A) Full Scale IP(max) 0A Accuracy 25C 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 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 device 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 device, 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. Primary Current I (%) 90 Transducer Output 10 0 t tPO (s) Rise Time, tr Step Response Power on Time versus External Filter Capacitance 200 180 160 140 120 100 80 60 40 20 0 TA=25C IP = 5 A IP = 0 A 0 10 20 CF (nF) 30 40 Output (mV) 50 Noise vs. Filter Cap 15 A Noise versus External Filter Capacitance 10000 Excitation Signal 100 10 1 0.01 0.1 1 CF (nF) 10 100 1000 tr(s) Rise Time versus External Filter Capacitance 1200 CF (nF) 1000 0 1 4.7 10 22 47 100 220 470 800 600 400 } Expanded in chart at right 200 0 0 100 200 300 CF (nF) 400 500 Rise Time versus External Filter Capacitance tr (s) 6.6 7.7 17.4 32.1 68.2 88.2 291.3 623.0 1120.0 tr(s) Noise(p-p) (mA) 1000 400 350 300 250 200 150 100 50 0 0 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 IC with 2.1 kVRMS 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 Amp Sample and Hold Hall Element 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Typical Applications +5 V +5 V VPEAK CBYP 0.1 F 1 2 IP IP+ VCC IP+ VIOUT 4 7 RF 10 k IP- FILTER IP- COUT 0.1 F VOUT 8 ACS712 3 CBYP 0.1 F C2 0.1 F GND 6 5 R4 10 k Q1 2N7002 1 + 2 - D1 U1 LT1178 1N914 R1 1 M CF 1 nF IP 4 R3 330 k C1 0.1 F VCC IP+ IP+ VIOUT R2 100 k 8 7 IP- FILTER IP- 1 + 3 - GND VOUT 4 2 C1 1000 pF R3 3.3 k 6 CF 0.01 F 5 LM321 5 RF 1 k ACS712 3 R2 33 k R1 100 k VRESET Application 3. This configuration increases gain to 610 mV/A (tested using the ACS712ELC-05A). Application 2. Peak Detecting Circuit +5 V +5 V CBYP 0.1 F R1 33 k CBYP 0.1 F 1 2 IP+ VCC IP+ VIOUT 8 7 RF 2 k ACS712 IP 3 4 IP- FILTER IP- GND VOUT 6 5 R1 10 k D1 1N4448W 1 2 A-to-D Converter IP C1 CF 1 nF 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. IP+ VCC IP+ VIOUT 8 7 VOUT 4 IP- FILTER IP- GND 4 3 ACS712 3 RPU 100 k R2 100 k 6 5 CF 1 nF - + 5 1 Fault 2 U1 LMV7235 D1 1N914 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 12 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 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 device. Such a lowpass filter improves the signal-to-noise ratio, and therefore the resolution, of the device output signal. However, the addition of an RC filter to the output of a sensor IC can result in undesirable device 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: RINTFC RF + RINTFC VATT = VIOUT . Even if RF and RINTFC are designed to match, the two individual resistance values will most likely drift by different amounts over 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 k. 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. +5 V Pin 3 Pin 4 IP- IP- VCC Pin 8 Allegro ACS706 Voltage Regulator To all subcircuits Filter 0.1 MF Resistive Divider VIOUT Pin 7 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. Amp Out N.C. Pin 6 Input RF Application Interface Circuit Low Pass Filter Temperature Coefficient Gain Offset CF 1 nF RINTFC Trim Control GND Pin 5 IP+ IP+ Pin 1 Pin 2 +5 V VCC Pin 8 Allegro ACS712 Hall Current Drive IP+ Pin 1 IP+ Pin 2 IP- Pin 3 IP- Pin 4 Sense Temperature Coefficient Trim Buffer Amplifier and Resistor 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. Signal Recovery VIOUT Pin 7 Input Application Interface Circuit Sense Trim 0 Ampere Offset Adjust 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 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor ACS712 Package LC, 8-pin SOIC 4.90 0.10 8 0 8 6.00 0.20 2 Branded Face 8X SEATING PLANE 0.10 C 1.27 BSC 1 1.27 0.40 0.25 BSC 0.51 0.31 5.60 1.04 REF A 1 C 1.27 1.75 0.25 0.17 3.90 0.10 8 0.65 C 2 PCB Layout Reference View SEATING PLANE GAUGE PLANE NNNNNNN TPP-AAA LLLLL 1.75 MAX 0.25 0.10 1 B Standard Branding Reference View For Reference Only; not for tooling use (reference MS-012AA) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area N = Device part number T = Device temperature range P = Package Designator A = Amperage L = Lot number Belly Brand = Country of Origin B Branding scale and appearance at supplier discretion C D Reference land pattern layout (reference IPC7351 SOIC127P600X175-8M); all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 ACS712 Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current Conductor Revision History Revision Revision Date Rev. 14 October 12, 2011 Description of Revision Update branding specifications Copyright (c)2006-2011, Allegro MicroSystems, Inc. The products described herein are protected by U.S. patents: 5,621,319; 7,598,601; and patent 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 15