Fully Integrated, Hall Effect-Based Linear Current Sensor with Features and Benefits Low-noise analog signal path Device bandwidth is set via the new pin 5 μs output rise time in response to step input current 5 khz bandwidth Total output error.5% at T A = 5 C, and % at C to 5 C Small footprint, low-profile SOIC package. mω internal conductor resistance. kv RMS minimum isolation voltage from pins - to pins 5-5. V, single supply operation to 5 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 Package: pin SOIC (suffix LC) Approximate Scale : Description The Allegro ACS provides economical and precise solutions for AC or DC current sensing in industrial, automotive, commercial, and communications systems. The device package allows for easy implementation by the customer. Typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection. 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 (>V IOUT(Q) ) when an increasing current flows through the primary copper conduction path (from pins and, to pins and ), which is the path used for current sensing. The internal resistance of this conductive path is. mω typical, providing low power Continued on the next page Typical Application I P ACS 5 V OUT nf C BYP. μf Application. The ACS outputs an analog signal, V OUT. that varies linearly with the uni- or bi-directional AC or DC primary sensed current, I P, within the range specified. is recommended for noise management, with values that depend on the application. ACS-DS, Rev.
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 ). This allows the ACS current sensor to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. The ACS is provided in a small, surface mount SOIC package. The leadframe is plated with % 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* T OP ( C) Optimized Range, I P (A) Sensitivity, Sens (Typ) (mv/a) ACSELCTR-5B-T Tape and reel, pieces/reel to 5 ±5 5 ACSELCTR-A-T Tape and reel, pieces/reel to 5 ± ACSELCTR-A-T Tape and reel, pieces/reel to 5 ± *Contact Allegro for additional packing options. Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Supply Voltage V CC V Reverse Supply Voltage V RCC. V Output Voltage V IOUT V Reverse Output Voltage V RIOUT. V Output Current Source I IOUT(Source) ma Output Current Sink I IOUT(Sink) ma total pulses, 5 ms duration each, applied Overcurrent Transient Tolerance I P at a rate of pulse every seconds. A Maximum Transient Sensed Current I R (max) Junction Temperature, T J < T J (max) A Nominal Operating Ambient Temperature T A Range E to 5 ºC Maximum Junction T J (max) 5 ºC Storage Temperature T stg 5 to ºC TÜV America Certificate Number: UV 5 5 Parameter Fire and Electric Shock Specification CAN/CSA-C. No. 95-- UL 95-: EN 95-: 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Functional Block Diagram (Pin ) Hall Current Drive (Pin ) Sense Temperature Coefficient Trim (Pin ) IP (Pin ) IP (Pin ) Dynamic Offset Cancellation Sense Trim Signal Recovery Ampere Offset Adjust R F(INT) (Pin ) (Pin 5) (Pin ) Pin-out Diagram 5 Terminal List Table Number Name Description and Terminals for current being sensed; fused internally and Terminals for current being sensed; fused internally 5 Signal ground terminal Terminal for external capacitor that sets bandwidth Analog output signal Device power supply terminal 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
COMMON OPERATING CHARACTERISTICS over full range of T OP, = nf, and V CC = 5 V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units ELECTRICAL CHARACTERISTICS Supply Voltage V CC.5 5. 5.5 V Supply Current I CC V CC = 5. V, output open ma Output Zener Clamp Voltage V Z I CC = ma, T A = 5 C. V Output Resistance R IOUT I IOUT =. ma, T A =5 C Ω Output Capacitance Load C LOAD to nf Output Resistive Load R LOAD to. kω Primary Conductor Resistance R PRIMARY T A = 5 C. mω RMS Isolation Voltage V ISORMS Pins - and 5-; Hz, minute, T A =5 C V DC Isolation Voltage V ISODC Pins - and 5-; minute, T A =5 C 5 V Propagation Time t PROP I P = I P (max), T A = 5 C, C OUT = open μs Response Time t RESPONSE I P = I P (max), T A = 5 C, C OUT = open μs Rise Time t r I P = I P (max), T A = 5 C, C OUT = open 5 μs Frequency Bandwidth f db, T A = 5 C; I P is A peak-to-peak 5 khz Nonlinearity E LIN Over full range of I P ± ±.5 % Symmetry E SYM Over full range of I P 9 % Zero Current Output Voltage V IOUT(Q) Bidirectional; I P = A, T A = 5 C V CC.5 V Magnetic Offset Error V ERROM I P = A, after excursion of 5 A mv V CH Typ. V CC.95 Clamping Voltage Typ. + mv V CL Typ. V CC.5 Typ. + mv Output reaches 9% of steady-state level, T Power-On Time t J = 5 C, A present PO on leadframe 5 μs Magnetic Coupling G/A Internal Filter Resistance R F(INT). kω Device may be operated at higher primary current levels, I P, and ambient, T A, and internal leadframe temperatures, T OP, provided that the Maximum Junction Temperature, T J (max), is not exceeded. G =. mt. R F(INT) forms an RC circuit via the pin. COMMON THERMAL CHARACTERISTICS Min. Typ. Max. Units Operating Internal Leadframe Temperature T OP E range 5 C Value Units Junction-to-Lead Thermal Resistance R θjl Mounted on the Allegro ASEK evaluation board 5 C/W Mounted on the Allegro 5- evaluation board, includes the power consumed by the board Junction-to-Ambient Thermal Resistance R θja C/W Additional thermal information is available on the Allegro website. The Allegro evaluation board has 5 mm of oz. copper on each side, connected to pins and, and to pins and, 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. 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
x5a PERFORMANCE CHARACTERISTICS T OP = C to 5 C, = nf, and V CC = 5 V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Optimized Accuracy Range I P 5 5 A Sens Sensitivity TA Over full range of I P, T A = 5 C 5 mv/a Sens TOP Over full range of I P 9 mv/a Peak-to-peak, T A = 5 C, 5 mv/a programmed Sensitivity, =. nf, C OUT = open, khz bandwidth 5 mv Noise V NOISE(PP) Peak-to-peak, T A = 5 C, 5 mv/a programmed Sensitivity, = nf, C OUT = open, khz bandwidth mv Peak-to-peak, T A = 5 C, 5 mv/a programmed Sensitivity, = nf, C OUT = open, 5 khz bandwidth 5 mv Electrical Offset Voltage V OE I P = A mv Total Output Error E TOT I P =±5 A, T A = 5 C ±.5 % Device may be operated at higher primary current levels, I P, and ambient temperatures, T OP, provided that the Maximum Junction Temperature, T J(max), is not exceeded. At C Sensitivity may shift as much 9% outside of the datasheet limits. Percentage of I P, with I P = 5 A. Output filtered. xa PERFORMANCE CHARACTERISTICS T OP = C to 5 C, = nf, and V CC = 5 V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Optimized Accuracy Range I P A Sens Sensitivity TA Over full range of I P, T A = 5 C mv/a Sens TOP Over full range of I P 9 mv/a Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, =. nf, C OUT = open, khz bandwidth mv Noise V NOISE(PP) Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, = nf, C OUT = open, khz bandwidth mv Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, = nf, C OUT = open, 5 khz bandwidth mv Electrical Offset Voltage V OE I P = A mv Total Output Error E TOT I P =± A, T A = 5 C ±.5 % Device may be operated at higher primary current levels, I P, and ambient temperatures, T OP, provided that the Maximum Junction Temperature, T J (max), is not exceeded. At C Sensitivity may shift as much 9% outside of the datasheet limits. Percentage of I P, with I P = A. Output filtered. xa PERFORMANCE CHARACTERISTICS T OP = C to 5 C, = nf, and V CC = 5 V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Optimized Accuracy Range I P A Sens Sensitivity TA Over full range of I P, T A = 5 C mv/a Sens TOP Over full range of I P mv/a Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, =. nf, C OUT = open, khz bandwidth mv Noise V NOISE(PP) Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, = nf, C OUT = open, khz bandwidth mv Peak-to-peak, T A = 5 C, mv/a programmed Sensitivity, = nf, C OUT = open, 5 khz bandwidth 5 mv Electrical Offset Voltage V OE I P = A mv Total Output Error E TOT I P = ± A, T A = 5 C ±.5 % Device may be operated at higher primary current levels, I P, and ambient temperatures, T OP, provided that the Maximum Junction Temperature, T J (max), is not exceeded. At C Sensitivity may shift as much 9% outside of the datasheet limits. Percentage of I P, with I P = A. Output filtered. 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5 5
Characteristic Performance I P = 5 A, Sens = 5 mv/a unless otherwise specified Mean I CC (ma) Mean Supply Current versus Ambient Temperature V CC = 5 V. 9.5 9..5..5..5. -5 5 5 I CC (ma) Supply Current versus Supply Voltage.5.. 9.9 9. 9.5 9. 9..9..5.5....9 5 5. 5. 5. 5. 5.5 V CC (V) V ERROM (mv) Magnetic Offset versus Ambient Temperature..5.5.5..5.5.5-5 5 5 E LIN (%) Nonlinearity versus Ambient Temperature I P = A.......... -5 5 5 Mean Total Output Error versus Ambient Temperature I P = A 5. Mean E TOT (%). 5.. -5. -. -5. -5 5 5 Output Voltage versus Sensed Current Sensitivity versus Sensed Current V IOUT (V).5..5..5..5..5 - - - - - Ip (A) 5 5 5 - Sens (mv/a)....... - - - - - Ip (A) 5 5-5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Characteristic Performance I P = A, Sens = mv/a unless otherwise specified Mean I CC (ma) Mean Supply Current versus Ambient Temperature V CC = 5 V. 9.5 9..5..5..5. -5 5 5 Magnetic Offset Current versus Ambient Temperature I CC (ma) Supply Current versus Supply Voltage.5.. 9.9 9. 9.5 9. 9..9..5.5....9 5 5. 5. 5. 5. 5.5 V CC (V) Nonlinearity versus Ambient Temperature V ERROM (mv)..... -5 5 5 E LIN (%).......... -5 5 5 Mean Total Output Error versus Ambient Temperature Mean E TOT (%) 5...... -. -. -. -. -5. -5 5 5 Output Voltage versus Sensed Current Sensitivity versus Sensed Current V IOUT (V).5..5..5..5..5 5 5 5-5. - - - - - - Ip (A) Ip (A) Sens (mv/a) 5.. 5.. 55. 5 5-5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Definitions of Accuracy Characteristics Sensitivity (Sens). The change in sensor output in response to a 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 (V NOISE ). The product of the linear IC amplifier gain (mv/g) and the noise floor for the Allegro Hall effect linear IC ( 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 (E LIN ). 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: Δ gain % sat ( V { [ IOUT_full-scale amperes V IOUT(Q) ) (V IOUT_half-scale amperes V IOUT(Q) ) where V IOUT_full-scale amperes = the output voltage (V) when the sensed current approximates full-scale ±I P. Symmetry (E SYM ). 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: V IOUT_+ full-scale amperes V IOUT(Q) V IOUT(Q) V IOUT_ full-scale amperes Quiescent output voltage (V IOUT(Q) ). The output of the sensor when the primary current is zero. For a unipolar supply voltage, it nominally remains at V CC. Thus, V CC = 5 V translates into V IOUT(Q) =.5 V. Variation in V IOUT(Q) can be attributed to the resolution of the Allegro linear IC quiescent voltage trim and thermal drift. Electrical offset voltage (V OE ). The deviation of the device output from its ideal quiescent value of V CC / due to nonmagnetic causes. To convert this voltage to amperes, divide by the device sensitivity, Sens. Accuracy (E TOT ). 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. { [ Accuracy is divided into four areas: A at 5 C. Accuracy of sensing zero current flow at 5 C, without the effects of temperature. A over Δ temperature. Accuracy of sensing zero current flow including temperature effects. Full-scale current at 5 C. Accuracy of sensing the full-scale current at 5 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 A output, V IOUT(Q), (nominally equal to V CC /) and sensitivity, Sens, are proportional to its supply voltage, V CC. The following formula is used to derive the ratiometric change in A output voltage, ΔV IOUT(Q)RAT (%). V IOUT(Q) / V IOUT(Q)5V V CC / 5 V The ratiometric change in sensitivity, ΔSens RAT (%), is defined as: I P (A) I P(min) Sens / Sens 5V V CC / 5 V Output Voltage versus Sensed Current Accuracy at A and at Full-Scale Current Accuracy Oe Temp v r erature Accuracy 5 C Only Accuracy 5 C Only Accuracy Oe Temp v r erature Increasing V IOUT (V) A Average V IOUT Accuracy 5 C Only Full Scale I P(max) Accuracy Oe Temp v r erature +I P (A) Decreasing V IOUT (V) 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Definitions of Dynamic Response Characteristics Propagation delay (t PROP ). The time required for the sensor output to reflect a change in the primary current signal. Propagation delay is attributed to inductive loading within the linear IC package, as well as in the inductive loop formed by the primary conductor geometry. Propagation delay can be considered as a fixed time offset and may be compensated. I (%) 9 Primary Current Transducer Output Propagation Time, t PROP t Response time (t RESPONSE ). The time interval between a) when the primary current signal reaches 9% of its final value, and b) when the sensor reaches 9% of its output corresponding to the applied current. I (%) 9 Primary Current Transducer Output Response Time, t RESPONSE t Rise time (t r ). The time interval between a) when the sensor reaches % of its full scale value, and b) when it reaches 9% 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( db) =.5 / t r. Both t r and t RESPONSE are detrimentally affected by eddy current losses observed in the conductive IC ground plane. I (%) 9 Primary Current Transducer Output Rise Time, t r t t PO (μs) Power on Time versus External Filter Capacitance I P =5 A I P = A 5 (nf) Noise vs. Filter Cap Noise versus External Filter Capacitance Step Response T A =5 C Output (mv) 5 A Excitation Signal Noise (p-p) (ma) t r (μs).. (nf) Rise Time versus External Filter Capacitance } Expanded in chart at right 5 (nf) (nf) t r (μs)....... 9... t r (μs) Rise Time versus External Filter Capacitance 5 5 5 5 5 5 5 (nf) 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5 9
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. Hall Element Regulator Clock/Logic Amp Sample and Hold Concept of Chopper Stabilization Technique Low-Pass Filter Typical Applications V PEAK I P C BYP. μf ACS 5 I P R F kω ACS 5 C OUT. μf V OUT R MΩ nf R kω Application. Peak Detecting Circuit C BYP. μf R F kω V OUT + R kω nf R kω C. μf R kω U LT D NW C D N9 C. μf V RESET Q N A-to-D Converter Application. Rectified Output.. V scaling and rectification application for A-to-D converters. Replaces current transformer solutions with simpler ACS circuit. C is a function of the load resistance and filtering desired. R can be omitted if the full range is desired. I P C BYP. μf ACS 5 I P C BYP. μf R kω R + kω LM 5 ACS 5 R F kω. μf R kω R kω V OUT nf R. kω + 5 U LMV5 D N9 V OUT C pf Application. This configuration increases gain to mv/a (tested using the ACSELC-5A). R PU kω Application 5. A Overcurrent Fault Latch. Fault threshold set by R and R. This circuit latches an overcurrent fault and holds it until the 5 V rail is powered down. Fault 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Improving Sensing System Accuracy Using the 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, V ATT, is a result of the resistive divider effect between the resistance of the external filter, R F (see Application ), and the input impedance and resistance of the customer interface circuit, R INTFC. The transfer function of this resistive divider is given by: R INTFC V ATT = V IOUT. R F + R INTFC Even if R F and R INTFC 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, R INTFC, of a typical analog-to-digital converter (ADC) can be as low as kω. The ACS contains an internal resistor, a 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, (see Application ) from the pin to ground. The buffer amplifier inside of the ACS (located after the internal resistor and pin connection) eliminates the attenuation caused by the resistive divider effect described in the equation for V ATT. Therefore, the ACS 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. Pin Pin Pin Application. When a low pass filter is constructed externally to a standard Hall effect device, a resistive divider may exist between the filter resistor, R F, and the resistance of the customer interface circuit, R INTFC. This resistive divider will cause excessive attenuation, as given by the transfer function for V ATT.. F Dynamic Offset Cancellation Voltage Regulator Amp To all subcircuits Filter Allegro ACS Out Pin N.C. Pin R F Resistive Divider Input Application Interface Circuit Low Pass Filter Gain Temperature Coefficient Offset nf R INTFC Trim Control Pin Pin Pin 5 Pin Application. Using the pin provided on the ACS eliminates the attenuation effects of the resistor divider between R F and R INTFC, shown in Application. Pin Pin Pin Pin Hall Current Drive Dynamic Offset Cancellation Sense Temperature Coefficient Trim Sense Trim Signal Recovery Ampere Offset Adjust Buffer Amplifier and Resistor Allegro ACS Pin Input Application Interface Circuit R INTFC Pin 5 Pin nf 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5
Package LC, -pin SOIC. 5....5 [.] M B M 5..9..9 A B º º.5... A Preliminary dimensions, for reference only Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only (reference JEDEC MS- AA) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown Terminal # mark area A...5.5...5..5. X. [.] C SEATING PLANE C SEATING PLANE GAUGE PLANE.5. X...5 [.] M C A B..5.5..5.5...9.5 Package Branding Two alternative patterns are used Text Text Text 5 ACST RLCPPP YYWWA ACS Allegro Current Sensor Device family number T Indicator of % matte tin leadframe plating R Operating ambient temperature range code LC Package type designator PPP Primary sensed current YY Date code: Calendar year (last two digits) WW Date code: Calendar week A Date code: Shift code ACST RLCPPP L...L YYWW ACS Allegro Current Sensor Device family number T Indicator of % matte tin leadframe plating R Operating ambient temperature range code LC Package type designator PPP Primary sensed current L...L Lot code YY Date code: Calendar year (last two digits) WW Date code: Calendar week The products described herein are manufactured under one or more or manufacturability of its products. Before placing an order, of the following U.S. patents: 5,5,9; 5,,; 5,,; the user is cautioned to verify that the information being relied 5,9,9; 5,5,9; 5,5,; 5,9,; 5,,9; 5,5,9; upon is current. The in for ma tion in clud ed herein is believed to 5,,9; 5,9,; 5,9,; 5,9,; and other patents be ac cu rate and reliable. How ev er, pending. assumes no re spon si bil i ty for its use; nor for any in fringe ment of reserves the right to make, from time patents or other rights of third parties which may result from its to time, such de par tures from the detail spec i fi ca tions as may be use. required to permit improvements in the per for mance, reliability, Copyright, For the latest version of this document, go to our website at: 5 Northeast Cutoff, Box 5 Worcester, Massachusetts 5- (5) 5-5