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| ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Features and Benefits Industry-leading noise performance with 120 kHz bandwidth through proprietary amplifier and filter design techniques Integrated shield greatly reduces capacitive coupling from current conductor to die due to high dV/dt, and prevents offset drift in high-side applications Small footprint surface mount QSOP24 package 2100 VRMS isolation voltage between primary current path and sensor IC electronics 1.1 m primary conductor resistance for low power loss User-settable Overcurrent Fault level Overcurrent Fault signal typically responds to an overcurrent condition in < 2 s Filter pin capacitor sets analog signal bandwidth 2% typical output error 3 to 5.5 V, single supply operation Factory trimmed sensitivity, quiescent output voltage, and associated temperature coefficients Chopper stabilization results in extremely stable quiescent output voltage Ratiometric output from supply voltage Description The Allegro(R) ACS709 current sensor IC provides economical and precise means for current sensing applications in industrial, automotive, commercial, and communications systems. The device is offered in a small footprint surface mount package that allows easy implementation in customer applications. The ACS709 consists of a precision linear Hall sensor integrated circuit with a copper conduction path located near the surface of the silicon die. Applied current flows through the copper conduction path, and the analog output voltage from the Hall sensor IC linearly tracks the magnetic field generated by the applied current. The accuracy of the ACS709 is maximized with this patented packaging configuration because the Hall element is situated in extremely close proximity to the current to be measured. High level immunity to current conductor dV/dt and stray electric fields, offered by Allegro proprietary integrated shield technology, guarantees low output ripple and low offset drift in high-side applications. The voltage on the Overcurrent Input (VOC pin) allows customers to define an overcurrent fault threshold for the device. When the current flowing through the copper conduction path (between the IP+ and IP- pins) exceeds this threshold, Continued on the next page... Package: 24 pin QSOP (suffix LF) Approximate Scale Typical Application 1 2 3 4 5 6 IP 7 8 9 10 11 12 IP+ IP+ IP+ IP+ IP+ IP+ IP- IP- IP- IP- IP- IP- NC 24 FAULT_EN NC 23 Fault_EN 22 21 20 19 18 17 16 15 1 nF A COC VIOUT CF RL 330 k B 0.1 F RH VCC ACS709 VOC VCC RH, RL CF COC A B Sets resistor divider reference for VOC Noise and bandwidth limiting filter capacitor Fault delay setting capacitor, 22 nF maximum Use of capacitor required Use of resistor optional FAULT VIOUT FILTER VZCR GND NC 14 NC 13 ACS709-DS ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package outputs. This allows the ACS709 family of sensor ICs to be used in applications requiring electrical isolation, without the use of opto-isolators or other costly isolation techniques. Applications include: * Motor control and protection * Load management and overcurrent detection * Power conversion and battery monitoring / UPS systems Description (continued) the open drain Overcurrent Fault pin will transition to a logic low state. Factory programming of the linear Hall sensor IC inside of the ACS709 results in exceptional accuracy in both analog and digital output signals. The internal resistance of the copper path used for current sensing is typically 1.1 m, for low power loss. Also, the current conduction path is electrically isolated from the low voltage device inputs and Selection Guide Part Number ACS709LLFTR-35BB-T ACS709LLFTR-20BB-T IP(LIN) (A) 75 37.5 Sens (Typ at VCC = 5 V) (mV/A) 28 56 TA (C) -40 to 150 Packing* Tape and Reel, 2500 pieces per reel *Contact Allegro for packing options. Absolute Maximum Ratings Characteristic Supply Voltage Filter Pin Analog Output Pin Overcurrent Input Pin L Overcurrent Pin FAU T Fault Enable (FAULT_EN) Pin Voltage Reference Output Pin DC Reverse Voltage: Supply Voltage, Filter, Analog Output, Overcurrent Input, Overcurrent Fault, Fault Enable, and Voltage Reference Output Pins Isolation Voltage Output Current Source Output Current Sink Operating Ambient Temperature Junction Temperature Storage Temperature Symbol VCC VFILTER VIOUT VOC V L FAU T VFAULTEN VZCR VRdcx VISO IIOUT(Source) IIOUT(Sink) TA TJ(max) Tstg Range L 60 Hz AC, TA = 25C, 1 minute Notes Rating 8 8 32 8 8 8 8 -0.5 2100 3 1 -40 to 150 165 -65 to 170 Units V V V V V V V V VAC mA mA C C C Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Functional Block Diagram VCC D Q CLK R FAULT_EN VOC Hall Bias POR POR FAULT Reset - + 2VREF Control Logic Drain FAULT 3 mA Fault Comparator - IP+ Sensitivity Trim VZCR + Signal Recovery Hall Amplifier VIOUT RF(INT) IP- VOUT(Q) Trim GND FILTER Terminal List Table Number 1 through 6 Name IP+ IP- NC GND VZCR FILTER VIOUT L FAU T VCC VOC Description Sensed current copper conduction path pins. Terminals for current being sensed; fused internally, loop to IP- pins; unidirectional or bidirectional current flow. Sensed current copper conduction path pins. Terminals for current being sensed; fused internally, loop to IP+ pins; unidirectional or bidirectional current flow. No connection Device ground connection. Voltage Reference Output pin. Zero current (0 A) reference; output voltage on this pin scales with VCC . Filter pin. Terminal for an external capacitor connected from this pin to GND to set the device bandwidth. Analog Output pin. Output voltage on this pin is proportional to current flowing through the loop between the IP+ pins and IP- pins. Overcurrent Fault pin. When current flowing between IP+ pins and IP- pins exceeds the overcurrent fault threshold, this pin transitions to a logic low state. Supply voltage. Overcurrent Input pin. Analog input voltage on this pin sets the overcurrent fault threshold. Pin-out Diagram IP+ 1 IP+ 2 IP+ 3 IP+ 4 IP+ 5 IP+ 6 IP- 7 IP- 8 IP- 9 IP- 10 IP- 11 IP- 12 24 NC 23 NC 22 FAULT_EN 21 VOC 20 VCC 19 FAULT 18 VIOUT 17 FILTER 16 VZCR 15 GND 14 NC 13 NC 7 through 12 13, 14, 23, 24 15 16 17 18 19 20 21 22 L FAULT_EN Enables overcurrent faulting when high. Resets when low. FAU T Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package COMMON OPERATING CHARACTERISTICS Valid at TA = -40C to 150C, VCC = 5 V, unless otherwise specified Characteristic ELECTRICAL CHARACTERISTICS Supply Voltage1 Nominal Supply Voltage Supply Current Output Capacitance Load Output Resistive Load Magnetic Coupling from Device Conductor to Hall Element Internal Filter Resistance2 Symbol VCC VCCN ICC CLOAD RLOAD MCHALL RF(INT) TA = 25C IP = IP0A IP = IP0A IP = 0 A, TA = 25C TA = 25C, Swing IP from 0 A to IP0A, no capacitor on FILTER pin, 100 pF from VIOUT to GND TA = 25C, no capacitor on FILTER pin, 100 pF from VIOUT to GND TA = 25C, Swing IP from 0 A to IP0A, no capacitor on FILTER pin, 100 pF from VIOUT to GND -3 dB, TA = 25C, no capacitor on FILTER pin, 100 pF from VIOUT to GND Output reaches 90% of steady-state level, no capacitor on FILTER pin, TA = 25C L VIOUT open, pin high FAU T VIOUT pin to GND VIOUT pin to GND Current flowing from IP+ to IP- pins Test Conditions Min. 3 - - - 10 - - - -0.75 99.1 - Typ. - 5 11 - - 9.5 1.7 1.1 0.25 100 VCCx0.5 Max. 5.5 - 14.5 10 - - - - 0.75 100.9 - Units V V mA nF k G/A k m % % V Primary Conductor Resistance RPRIMARY ANALOG OUTPUT SIGNAL CHARACTERISTICS Full Range Linearity3 ELIN Symmetry4 ESYM Bidirectional Quiescent Output VOUT(QBI) TIMING PERFORMANCE CHARACTERISTICS VIOUT Signal Rise Time VIOUT Signal Propagation Time VIOUT Signal Response Time VIOUT Large Signal Bandwidth5 Power-On Time OVERCURRENT CHARACTERISTICS Setting Voltage for Overcurrent Switchpoint6 Signal Noise at Overcurrent Comparator Input Overcurrent Fault Switchpoint Error7,8 L Overcurrent Pin Output Voltage FAU T Fault Enable (FAULT_EN Pin) Input Low Voltage Threshold Fault Enable (FAULT_EN Pin) Input High Voltage Threshold Fault Enable (FAULT_EN Pin) Input Resistance tr tPROP tRESPONSE f3dB tPO VOC INCOMP EOC V L FAU T VIL VIH RFEI - - - - - VCCx0.25 - 3 1 4 120 35 - 1 5 - - - 1 - - - - - VCCx0.4 - - 0.4 0.1 x VCC - - s s s kHz s V A % V V V M Switchpoint in VOC safe operating area; assumes INCOMP = 0 A L 1 mA sink current at pin FAU T - - - 0.8 x VCC - Continued on the next page... Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package COMMON OPERATING CHARACTERISTICS (continued) Valid at TA = -40C to 150C, VCC = 5 V, unless otherwise specified Characteristic Symbol OVERCURRENT CHARACTERISTICS (continued) Overcurrent Fault Response Time tOC Test Conditions Switchpoint set at 90% of IPOA, delay from IP exceeding overcurrent fault threshold to V < 0.4 V, without L FAU T external COC capacitor Time from VFAULTEN < VIL to VFAULT > 0.8 x VCC , RPU = 330 k Time from VFAULTEN pin < VIL to reset of fault latch; see Functional Block Diagram TA = 25C, VOC pin to GND TA = 25 C Source current Sink current Min. Typ. Max. Units - 1.9 - s Overcurrent Fault Reset Delay Overcurrent Fault Reset Hold Time Overcurrent Input Pin Resistance VOLTAGE REFERENCE CHARACTERISTICS Voltage Reference Output tOCR tOCH ROC VZCR - - 2 500 250 - - - - ns ns M - 0.5 x VCC - V 3 - - mA Voltage Reference Output Load Current IZCR 50 - - A Voltage Reference Output Drift VZCR - 10 - mV 1Devices are trimmed for maximum accuracy at V CC = 5 V. The ratiometry feature of the device allows operation over the full VCC range; however, accuracy may be slightly degraded for VCC values other than 5 V. Contact the Allegro factory for applications that require maximum accuracy for VCC = 3.3 V. 2R F(INT) forms an RC circuit via the FILTER pin. 3This parameter can drift by as much as 0.25% over the lifetime of this product. 4This parameter can drift by as much as 0.3% over the lifetime of this product. 5Calculated using the formula f 3dB = 0.35 / tr . 6See page 8 on how to set overcurrent fault switchpoint. 7Switchpoint can be lower at the expense of switchpoint accuracy. 8This error specification does not include the effect of noise. See the I NCOMP specification in order to factor in the additional influence of noise on the fault switchpoint. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package X20B PERFORMANCE CHARACTERISTICS, TA Range L, valid at TA = - 40C to 150C, VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Linear Sensing Range Noise1 Sensitivity2,3 Symbol IP(OA) IP(LIN) VNOISE(rms) TA = 25C, Sens = 56 mV/A, Cf = 0, CLOAD = 4.7 nF, RLOAD open IP = 12.5 A, TA = 25C Sens IP = 12.5 A, TA = 25C to 150C IP = 12.5 A, TA = - 40C to 25C IP = 0 A, TA = 25C Electrical Offset Voltage2 VOE IP = 0 A, TA = 25C to 150C IP = 0 A, TA = - 40C to 25C Total Output Error2,4 1V Test Conditions Min. -20 -37.5 - - 54.5 54.5 - -25 -40 - - Typ. - - 1.50 56 - - 5 - - 2 3 Max. 20 37.5 - - 58 58.5 - 25 40 - - Units A A mV mV/A mV/A mV/A mV mV mV % % Performance Characteristics at VCC = 5 V ETOT Tested at IP =12.5 A, IP applied for 5 ms, TA = 25C to 150C Tested at IP =12.5 A, IP applied for 5 ms, TA = - 40C to 25C pk-pk noise (6 sigma noise) is equal to 6 x VNOISE(rms). Lower noise levels than this can be achieved by using Cf for applications requiring narrower bandwidth. See Characteristic Performance page for graphs of noise versus Cf and bandwidth versus Cf. 2See Characteristic Performance Data graphs for parameter distribution over ambient temperature range. 3This parameter can drift by as much as 1.75% over lifetime of the product. 4This parameter can drift by as much as 2.5% over lifetime of the product. X35B PERFORMANCE CHARACTERISTICS, TA Range L, valid at TA = - 40C to 150C, VCC = 5 V, unless otherwise specified Characteristic Optimized Accuracy Range Linear Sensing Range Noise1 Sensitivity2,3 Symbol IP(OA) IP(LIN) VNOISE(rms) TA = 25C, Sens = 28 mV/A, Cf = 0, CLOAD = 4.7 nF, RLOAD open IP = 25 A, TA = 25C Sens IP = 25 A, TA = 25C to 150C IP = 25 A, TA = - 40C to 25C IP = 0 A, TA = 25C Electrical Offset Voltage2 VOE IP = 0 A, TA = 25C to 150C IP = 0 A, TA = - 40C to 25C Total Output Error2,4 1V pk-pk Test Conditions Min. -37.5 -75 - - 27 27 - -25 -40 - - Typ. - - 1 28 - - 5 - - 3 3 Max. 37.5 75 - - 29.5 29.5 - 25 40 - - Units A A mV mV/A mV/A mV/A mV mV mV % % Performance Characteristics at VCC = 5 V ETOT Tested at IP = 25 A, IP applied for 5 ms, TA = 25C to 150C Tested at IP = 25 A, IP applied for 5 ms, TA = - 40C to 25C noise (6 sigma noise) is equal to 6 x VNOISE(rms). Lower noise levels than this can be achieved by using Cf for applications requiring narrower bandwidth. See Characteristic Performance page for graphs of noise versus Cf and bandwidth versus Cf. 2See Characteristic Performance Data graphs for parameter distribution over ambient temperature range. 3This parameter can drift by as much as 1.75% over lifetime of the product. 4This parameter can drift by as much as 2.5% over lifetime of the product. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Thermal Characteristics Characteristic Steady State Package Thermal Resistance Symbol RJA Test Conditions Tested with 30 A DC current and based on ACS709 demo board in 1 cu. ft. of still air. Please refer to product FAQs page on Allegro web site for detailed information on ACS709 demo board. Tested with 30 A DC current and based on ACS709 demo board in 1 cu. ft. of still air. Please refer to product FAQs page on Allegro web site for detailed information on ACS709 demo board. Value 21 Units C/W Transient Package Thermal Resistance RTJA See graph C/W ACS709 Transient Package Thermal Resistance On 85--0444 Demo Board (No Al Plate) 22 20 18 Thermal Resistance (C/W) 16 14 12 10 8 6 4 2 0 0.01 0.1 1 Time (Sec) 10 100 1000 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Characteristic Performance ACS709 Bandwidth versus External Capacitor Value, CF Capacitor connected between FILTER pin and GND 1000 100 Bandwidth (kHz) 10 1 0.1 0.01 0.1 1 Capacitance (nF) 10 100 1000 ACS709 Noise versus External Capacitor Value, CF Capacitor connected between FILTER pin and GND ACS709x-35B V CC = 5 V 1000 900 RMS Noise (V) 800 700 600 500 400 0 10 20 30 40 50 Capacitance (nF) RMS Noise (V) 900 800 700 600 500 400 300 0 10 20 30 40 50 Capacitance (nF) ACS709x-35B V CC = 3.3 V 1600 1400 RMS Noise (V) ACS709x-20B V CC = 5 V 1600 1400 RMS Noise (V) 1200 1000 800 600 400 200 0 ACS709x-20B V CC = 3.3 V 1200 1000 800 600 400 200 0 0 10 20 30 40 50 0 10 20 30 40 50 Capacitance (nF) Capacitance (nF) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Characteristic Performance Data Data taken using the ACS709-20BB, VCC = 5 V Accuracy Data Electrical Offset Voltage versus Ambient Temperature 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -50 58.0 57.5 Sensitivity versus Ambient Temperature Sens (mV/A) VOE (mV) 57.0 56.5 56.0 55.5 55.0 -50 -25 0 25 50 TA (C) 75 100 125 150 -25 0 25 50 TA (C) 75 100 125 150 Nonlinearity versus Ambient Temperature 0.20 0.15 0.10 0 -0.05 -0.10 -0.15 -0.20 -0.25 -0.30 -50 99.4 -25 0 25 50 TA (C) 75 100 125 150 -50 0.05 100.8 100.6 100.4 Symmetry versus Ambient Temperature ESYM (%) ELIN (%) 100.2 100.0 99.8 99.6 -25 0 25 50 TA (C) 75 100 125 150 Total Output Error versus Ambient Temperature 4 3 2 1 ETOT (%) 0 -1 -2 -3 -4 -50 -25 0 25 50 TA (C) 75 100 125 150 Typical Maximum Limit Mean Typical Minimum Limit Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Characteristic Performance Data Data taken using the ACS709-35BB, VCC = 5 V Accuracy Data Electrical Offset Voltage versus Ambient Temperature 20 15 5 0 -5 -10 -15 -20 -25 -50 -25 0 25 50 TA (C) 75 100 125 150 10 29.0 28.8 Sensitivity versus Ambient Temperature Sens (mV/A) 28.6 28.4 28.2 28.0 27.8 27.6 27.4 -50 -25 0 25 50 TA (C) 75 100 125 150 VOE (mV) Nonlinearity versus Ambient Temperature 0.30 0.20 101.0 100.8 100.6 100.4 100.2 100.0 99.8 99.6 99.4 99.2 -0.30 -50 -25 0 25 50 TA (C) 75 100 125 150 99.0 -50 Symmetry versus Ambient Temperature 0 -0.10 -0.20 ESYM (%) ELIN (%) 0.10 -25 0 25 50 TA (C) 75 100 125 150 Total Output Error versus Ambient Temperature 4 3 2 1 ETOT (%) 0 -1 -2 -3 -4 -50 -25 0 25 50 TA (C) 75 100 125 150 Typical Maximum Limit Mean Typical Minimum Limit Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Setting Overcurrent Fault Switchpoint The VOC needed for setting the overcurrent fault switchpoint can be calculated as follows: VOC = Sens x | IOC | , where VOC is in mV, Sens in mV/A, and IOC (overcurrent fault switchpoint) in A. | Ioc | is the overcurrent fault switchpoint for a bidirectional (AC) current, which means a bi-directional device will have two symmetrical overcurrent fault switchpoints, +IOC and -IOC . See the following graph for IOC and VOC ranges. IOC versus VOC IOC 0.4 VCC / Sens Not in Valid Range In Valid Range 0.25 VCC / Sens 0 0. 25 VCC - 0.25 VCC / Sens 0. 4 VCC VOC - 0.4 VCC / Sens Example: For ACS709LLFTR-35BB-T, if required overcurrent fault switchpoint is 50 A, and VCC = 5 V, then the required VOC can be calculated as follows: VOC = Sens x IOC = 28 x 50 = 1400 (mV) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Functional Description Overcurrent Fault Operation The primary concern with high-speed fault detection is that noise may cause false tripping. Various applications have or need to be able to ignore certain faults that are due to switching noise or other parasitic phenomena, which are application dependant. The problem with simply trying to filter out this noise up front is that in high-speed applications, with asymmetric noise, the act of filtering introduces an error into the measurement. To get around this issue, and allow the user to prevent the fault signal from being latched by noise, a circuit was designed to slew the FAULT pin voltage based on the value of the capacitor from that pin to ground. Once the voltage on the pin falls below 2 V, as established by an internal reference, the fault output is latched and pulled to ground quickly with an internal N-channel MOSFET. Fault Walk-through The following walk-through references various sections and attributes in the figure below. This figure shows different fault set/reset scenarios and how they relate to the voltages on the pin, FAULT_EN pin, and the internal Overcurrent FAULT (OC) Fault node, which is invisible to the customer. 1.Because the device is enabled (FAULT_EN is high) and there is an OC fault condition, the device pin starts discharging. FAULT 2. When the pin voltage reaches approximately 2 V, the FAULT fault is latched, and an internal NMOS device pulls the FAULT pin voltage to approximately 0 V. The rate at which the FAULT pin slews downward (see [4] in the figure) is dependent on the FAULT external capacitor, COC, on the pin. 3.When the FAULT_EN pin is brought low, the pin starts FAULT resetting if no OC Fault condition exists. The internal NMOS pull-down turns off and an internal PMOS pull-up turns on (see [7] if the OC Fault condition still exists). 4. The slope, and thus the delay, on the fault is controlled by the capacitor, COC, placed on the pin to ground. During this FAULT portion of the fault (when the pin is between VCC and FAULT 2 V), there is a 3 mA constant current sink, which discharges COC. The length of the fault delay, t, is equal to: t= COC ( VCC - 2 V ) 3 mA (1) where VCC is the device power supply voltage. 5. The pin did not reach the 2 V latch point before FAULT the OC fault condition cleared. Because of this, the fixed 3 mA current sink turns off, and the internal PMOS pull-up turns on to recharge COC through the pin. FAULT VCC 1 1 4 4 6 1 4 6 2 5 2 7 3 6 8 4 2 FAULT (Output) 2V 0V Time FAULT_EN (Input) OC Fault Condition (Active High) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package 6. This curve shows VCC charging external capacitor COC through the internal PMOS pull-up. The slope is determined by COC. When the FAULT_EN pin is brought low, if the fault condi tion still exists, the latched pin will stay low until FAULT the fault condition is removed, then it will start resetting. At this point there is a fault condition, and the part is enabled before the pin can charge to VCC. This shortens the FAULT user-set delay, so the fault is latched earlier. The new delay time can be calculated by equation 1, after substituting the voltage seen on the pin for VCC. FAULT 7. 8. 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 Sample and Hold Low-Pass Filter Amp 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 13 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package 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 device 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 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 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 VIOUT(Q)VCC / VIOUT(Q)5V {[ VIOUT_full-scale amperes - VIOUT(Q) 2 (VIOUT_1/2 full-scale amperes - VIOUT(Q) ) [{ VCC / 5 V The ratiometric change in sensitivity, SensRAT (%), 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 device 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 VIOUT(Q) - VIOUT_-full-scale amperes Accuracy Over Temp erature 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 0.5xVCC. For example, in the case of a bidirectional output device, 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 voltage 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. Note that error is directly measured during final test at Allegro. -IP (A) Average VIOUT Accuracy 25C Only IP(min) +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 14 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Definitions of Dynamic Response Characteristics I (%) Primary Current Propagation delay (tPROP). The time required for the device 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. 90 Transducer Output 0 Propagation Time, tPROP t I (%) Primary Current Response time (tRESPONSE). The time interval between a) when the primary current signal reaches 90% of its final value, and b) when the device reaches 90% of its output corresponding to the applied current. 90 Transducer Output 0 Response Time, tRESPONSE t I (%) Primary Current 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 current sensor IC, 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. 90 Transducer Output 10 0 Rise Time, tr t Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 15 ACS709 High Bandwidth, Fast Fault Response Current Sensor IC In Thermally Enhanced Package Package LF, 24-pin QSOP 8.66 0.10 24 8 0 0.25 0.15 2.30 3.91 0.10 A 5.99 0.20 5.00 1.27 0.41 1 2 Branded Face 24X 0.20 C 0.30 0.20 0.635 BSC 0.25 MAX 1.75 MAX C 1.04 REF 0.25 BSC SEATING PLANE GAUGE PLANE 0.40 B 0.635 PCB Layout Reference View SEATING PLANE NNNNNNNNNNNNN TLF-AAA LLLLLLLLLLL For Reference Only, not for tooling use (reference JEDEC MO-137 AE) 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 B Reference pad layout (reference IPC7351 SOP63P600X175-24M) C Standard Branding Reference View N = Device part number T = Temperature code LF = (Literal) Package type A = Amperage All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances C Branding scale and appearance at supplier discretion Copyright (c)2008-2009, Allegro MicroSystems, Inc. The products described herein are protected by U.S. patents: 7,166,807; 7,425,821; 7,573,393; and 7,598,601. 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 16 |
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