Features and Benefits Industry-leading noise performance through proprietary amplifier and filter design techniques Integrated shield greatly reduces capacitive coupling from current conductor to die due to high dv/dt signals, and prevents offset drift in high-side, high voltage applications Total output error improvement through gain and offset trim over temperature Small package size, with easy mounting capability Monolithic Hall IC for high reliability Ultra-low power loss: μω internal conductor resistance Galvanic isolation allows use in economical, high-side current sensing in high voltage systems 3. to. V, single supply operation Continued on the next page PSS Leadform TÜV America Certificate Number: U8V 9 424 2 Package: -pin package PFF Leadform Additional leadforms available for qualifying volumes Description The Allegro ACS78 family of current sensor ICs provides economical and precise solutions for AC or DC current sensing. Typical applications include motor control, load detection and management, power supply and DC-to-DC converter control, inverter control, and overcurrent fault detection. The device consists of a precision, low-offset linear Hall circuit with a copper conduction path located near 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 output voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC, which is programmed for accuracy at the factory. High level immunity to current conductor dv/dt and stray electric fields, offered by Allegro proprietary integrated shield technology, guarantees low output voltage ripple and low offset drift in high-side, high voltage applications. The output of the device has a positive slope (>V CC / 2) when an increasing current flows through the primary copper conduction path (from terminal 4 to terminal ), which is the path used for current sampling. The internal resistance of this conductive path is μω typical, providing low power loss. The thickness of the copper conductor allows survival of the device at high overcurrent conditions. The terminals of the Continued on the next page Typical Application +3.3 or V I P 4 VCC IP+ ACS78 GND 2 C BYP. μf IP VIOUT 3 R F C F V OUT Application. The ACS78 outputs an analog signal, V OUT, that varies linearly with the uni- or bi-directional AC or DC primary sampled current, I P, within the range specified. C F is for optimal noise management, with values that depend on the application. ACS78-DS, Rev. 4
Features and Benefits (continued) 2 khz typical bandwidth 3 μs output rise time in response to step input current Output voltage proportional to AC or DC currents Factory-trimmed for accuracy Extremely stable output offset voltage Nearly zero magnetic hysteresis Description (continued) conductive path are electrically isolated from the signal leads (pins through 3). This allows the ACS78 family of sensor ICs to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. The device is fully calibrated prior to shipment from the factory. The ACS78 family is lead (Pb) free. All leads are plated with % matte tin, and there is no Pb inside the package. The heavy gauge leadframe is made of oxygen-free copper. Selection Guide Package Primary Sampled Sensitivity Part Number Current Current, I P Sens (Typ.) Terminals Signal Pins Directionality (A) (mv/a) ACS78LCB-B-PFF-T Formed Formed ± 4. Bidirectional ACS78LCB-U-PFF-T Formed Formed 6. Unidirectional ACS78LCB-B-PFF-T Formed Formed ± 2. Bidirectional ACS78LCB-U-PFF-T Formed Formed 4. Unidirectional ACS78KCB-B-PFF-T Formed Formed ± 3.3 Bidirectional ACS78KCB-U-PFF-T Formed Formed 26.7 Unidirectional ACS78KCB-B-PSS-T Straight Straight ± 3.3 Bidirectional ACS78ECB-2B-PFF-T Formed Formed ±2. Bidirectional ACS78ECB-2U-PFF-T Formed Formed 2 2. Unidirectional ACS78ECB-2B-PSS-T Straight Straight ±2. Bidirectional Additional leadform options available for qualified volumes. 2 Contact Allegro for additional packing options. T OP ( C) 4 to 4 to 2 4 to 8 Packing 2 34 pieces per tube 2
Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Forward Supply Voltage V CC 8 V Reverse Supply Voltage V RCC. V Working Voltage for Reinforced Isolation V WORKING-R tested at 3 VAC for minute according to Voltage applied between pins -3 and 4-; UL standard 69- Working Voltage for Basic Isolation V WORKING-B tested at 3 VAC for minute according to Voltage applied between pins -3 and 4-; UL standard 69-33 VDC / V pk VDC / V pk Forward Output Voltage V IOUT 28 V Reverse Output Voltage V RIOUT. V Output Source Current I OUT(Source) VIOUT to GND 3 ma Output Sink Current I OUT(Sink) VCC to VIOUT ma Nominal Operating Ambient Temperature T OP Range K 4 to 2 ºC Range E 4 to 8 ºC Range L 4 to ºC Maximum Junction T J (max) 6 ºC Storage Temperature T stg 6 to 6 ºC Thermal Characteristics may require derating at maximum conditions Characteristic Symbol Test Conditions* Value Unit Package Thermal Resistance R θja *Additional thermal information available on the Allegro website Mounted on the Allegro evaluation board with 28 mm 2 (4 mm 2 on component side and 4 mm 2 on opposite side) of 4 oz. copper connected to the primary leadframe and with thermal vias connecting the copper layers. Performance is based on current flowing through the primary leadframe and includes the power consumed by the PCB. 7 ºC/W Typical Overcurrent Capabilities,2 Characteristic Symbol Notes Rating Units Overcurrent I POC T A = 8 C, s duration, % duty cycle 9 A T A = 2 C, s duration, % duty cycle 2 A T A = C, s duration, % duty cycle 6 A Test was done with Allegro evaluation board. The maximum allowed current is limited by T J (max) only. 2 For more overcurrent profiles, please see FAQ on the Allegro website, www.allegromicro.com. 3
Functional Block Diagram +3.3 to V IP+ VCC To all subcircuits Dynamic Offset Cancellation Amp Filter Out VIOUT. μf Gain Gain Temperature Coefficient Offset Offset Temperature Coefficient Trim Control IP GND Pin-out Diagram IP+ 4 3 VIOUT 2 GND IP VCC Terminal List Table Number Name Description VCC Device power supply terminal 2 GND Signal ground terminal 3 VIOUT Analog output signal 4 IP+ Terminal for current being sampled IP Terminal for current being sampled 4
COMMON OPERATING CHARACTERISTICS valid at T OP = 4 C to C and V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Supply Voltage V CC 3.. V Supply Current I CC Output open 3. ma Power-On Delay t POD T A = 2 C μs Rise Time 2 t r I P step = 6% of I P +, % to 9% rise time, T A = 2 C, C OUT =.47 nf 3 μs Propagation Delay Time 2 t PROP T A = 2 C, C OUT =.47 nf μs Response Time t RESPONSE Measured as sum of t PROP and t r 4 μs Internal Bandwidth 3 BW i 3 db; T A = 2 C, C OUT =.47 nf 2 khz Output Load Resistance R LOAD(MIN) VIOUT to GND 4.7 kω Output Load Capacitance C LOAD(MAX) VIOUT to GND nf Primary Conductor Resistance R PRIMARY T A = 2 C μω Symmetry 2 E SYM Over half-scale of Ip 99 % Quiescent Output Voltage 4 Unidirectional variant, I V P = A, T A = 2 C, V IOUT(QUNI) is IOUT(QUNI) ratiometric to V CC.6 V V IOUT(QBI) Bidirectional variant, I P = A, T A = 2 C V CC /2 V Ratiometry 2 V RAT V CC = 4. to. V % Device is factory-trimmed at V, for optimal accuracy. 2 See Characteristic Definitions section of this datasheet. 3 Calculated using the formula BW i =.3 / t r. 4 V IOUT(Q) may drift over the lifetime of the device by as much as ±2 mv.
XB PERFORMANCE CHARACTERISTICS : T OP = 4 C to C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 4 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to C 39.4 mv/a Sens (TOP)LT Full scale of I P applied for ms,t OP = 4 C to 2 C 4 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to C ± mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±3 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to C.2 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C 2 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) = 2. V. 4 Percentage of I P. Output filtered. XU PERFORMANCE CHARACTERISTICS : T OP = 4 C to C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 6 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to C 9 mv/a Sens (TOP)LT Full scale of I P applied for ms,t OP = 4 C to 2 C 6 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to C ±2 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±4 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to C.2 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C 2 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) =. V. 4Percentage of I P. Output filtered. 6
XB PERFORMANCE CHARACTERISTICS : T OP = 4 C to C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 2 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to C 9.7 mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C 2. mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 6 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms.2.2 % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to C ±2 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±2 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to C.3 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C 2.4 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) = 2. V. 4 Percentage of I P. Output filtered. XU PERFORMANCE CHARACTERISTICS : T OP = 4 C to C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 4 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to C 39. mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C 4 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 2 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms.2.2 % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to C ±2 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±2 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to C.3 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C 2.4 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) =. V. 4Percentage of I P. Output filtered. 7
XB PERFORMANCE CHARACTERISTICS : T OP = 4 C to 2 C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 3.3 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to 2 C 3. mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C 3. mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 4 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to 2 C ±4 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±24 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A 2 ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to 2 C.8 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C.6 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) = 2. V. 4 Percentage of I P. Output filtered. XU PERFORMANCE CHARACTERISTICS : T OP = 4 C to 2 C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P A Sens TA Full scale of I P applied for ms, T A = 2 C 26.6 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to 2 C 26.6 mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C 27.4 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 8 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to 2 C ±4 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±24 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of A 2 ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to 2 C.8 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C.6 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) =. V. 4Percentage of I P. Output filtered. 8
X2B PERFORMANCE CHARACTERISTICS : T OP = 4 C to 8 C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P 2 2 A Sens TA Full scale of I P applied for ms, T A = 2 C mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to 8 C 9.88 mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C.3 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 3 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to 8 C ± mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±2 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of 2 A 23 ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to 8 C.2 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C.2 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) = 2. V. 4 Percentage of I P. Output filtered. X2U PERFORMANCE CHARACTERISTICS : T OP = 4 C to 8 C, V CC = V, unless otherwise specified Characteristic Symbol Test Conditions Min. Typ. Max. Units Primary Sampled Current I P 2 A Sens TA Full scale of I P applied for ms, T A = 2 C 2 mv/a Sensitivity Sens (TOP)HT Full scale of I P applied for ms, T OP = 2 C to 8 C 9.7 mv/a Sens (TOP)LT Full scale of I P applied for ms, T OP = 4 C to 2 C 2.3 mv/a Noise 2 V NOISE T A = 2 C, nf on VIOUT pin to GND 6 mv Nonlinearity E LIN Up to full scale of I P, I P applied for ms % Electrical Offset Voltage 3 V OE(TOP)HT I P = A, T OP = 2 C to 8 C ±2 mv V OE(TA) I P = A, T A = 2 C ± mv V OE(TOP)LT I P = A, T OP = 4 C to 2 C ±3 mv Magnetic Offset Error I ERROM I P = A, T A = 2 C, after excursion of 2 A 23 ma E Total Output Error 4 TOT(HT) Over full scale of I P, I P applied for ms, T OP = 2 C to 8 C.2 % E TOT(LT) Over full scale of I P, I P applied for ms, T OP = 4 C to 2 C.2 % See Characteristic Performance Data page for parameter distributions over temperature range. 2 ±3 sigma noise voltage. 3 V OE(TOP) drift is referred to ideal V IOUT(Q) =. V. 4Percentage of I P. Output filtered. 9
Characteristic Performance Data Data taken using the ACS78LCB-B Data Electrical Offset Voltage versus Ambient Temperature Sensitivity versus Ambient Temperature VOE (mv) 3 2 42. 42. 4. 4. - 4. -2-3 -4 - -2 2 7 2 39. 39. 38. -2 2 7 2 Sens (mv/a) Nonlinearity versus Ambient Temperature Symmetry versus Ambient Temperature ELIN (%).4.4.3.3.2.2... ESYM (%) 99.9-2 2 7 2-2 2 7 2.4.3.3.2.2.... IERROM (ma) 4 2 8 6 4 2 Magnetic Offset Error versus Ambient Temperature Total Output Error versus Ambient Temperature E TOT (%) -4-2 2 7 2-2 2 7 2 6 4 3 2 - -2-3 Typical Maximum Limit Mean Typical Minimum Limit
Characteristic Performance Data Data taken using the ACS78LCB-B Data Electrical Offset Voltage versus Ambient Temperature Sensitivity versus Ambient Temperature VOE (mv) 2 2 - - - -2-2 -2 2 7 2 Sens (mv/a) 2.2 2. 2.8 2.6 2.4 2.2 2. 9.8 9.6 9.4 9.2-2 2 7 2 Nonlinearity versus Ambient Temperature Symmetry versus Ambient Temperature ELIN (%).4.3.3.2.2... -2 2 7 2 E SYM (%).6..4.3.2.. 99.9 99.8 99.7-2 2 7 2 Magnetic Offset Error versus Ambient Temperature Total Output Error versus Ambient Temperature IERROM (ma) 2 9 8 7 6 3 2-2 2 7 2 ETOT (%) 6 4 3 2 - -2-3 -4 - -2 2 7 2 Typical Maximum Limit Mean Typical Minimum Limit
Characteristic Performance Data Data taken using the ACS78KCB-B Data Electrical Offset Voltage versus Ambient Temperature Sensitivity versus Ambient Temperature VOE (mv) 2 4. 3.8 3.6 3.4 - - - 3.2 3. -2-2 -3 6 4 2 2 4 6 8 2 4 2.8 2.6 6 4 2 2 4 6 8 2 4 Sens (mv/a) ELIN (%) Nonlinearity versus Ambient Temperature.3.2 2.... 6 4 2 2 4 6 8 2 4 E SYM (%) Symmetry versus Ambient Temperature.7.6..4.3.2.. 99.9 99.8 6 4 2 2 4 6 8 2 4 Magnetic Offset Error versus Ambient Temperature Total Output Error versus Ambient Temperature IERROM (ma) 3 2 2 ETOT (%) 4 3 2 - -2-3 -4 - -6 6 4 2 2 4 6 8 2 4 6 4 2 2 4 6 8 2 4 Typical Maximum Limit Mean Typical Minimum Limit 2
Characteristic Performance Data Data taken using the ACS78ECB-2B Data Electrical Offset Voltage versus Ambient Temperature Sensitivity versus Ambient Temperature VOE (mv) 2 2.4.3.2. - - - -2-2 -3 6 4 2 2 4 6 8 2 4. 9.9 9.8 9.7 9.6 9. 6 4 2 2 4 6 8 2 4 Sens (mv/a) Nonlinearity versus Ambient Temperature Symmetry versus Ambient Temperature ELIN (%).6.8.4.2.6..8.4.6.4.2.2. -.2 99.8 -.4 -.6 99.6 6 4 2 2 4 6 8 2 4 6 4 2 2 4 6 8 2 4 E SYM (%) Magnetic Offset Error versus Ambient Temperature Total Output Error versus Ambient Temperature IERROM (ma) 3 3 2 2 6 4 2 2 4 6 8 2 4 ETOT (%) 4 3 2 - -2-3 -4 - -6 6 4 2 2 4 6 8 2 4 Typical Maximum Limit Mean Typical Minimum Limit 3
Characteristic Performance Data Data taken using the ACS78LCB- Timing Data Rise Time Propagation Delay Time I P (2 A/div.) I P (2 A/div.) V IOUT (. V/div.) V IOUT (. V/div.) 2.988 μs 997 ns t (2 μs/div.) t (2 μs/div.) Response Time Power-on Delay V CC I P (2 A/div.) V IOUT (. V/div.) 9.34 μs 3.96 μs V IOUT ( V/div.) (I P = 6 A DC) t (2 μs/div.) t (2 μs/div.) 4
Definitions of Characteristics Characteristic Definitions Sensitivity (Sens). The change in device 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 half-scale current of the device. Noise (V NOISE ). 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. Nonlinearity (E LIN ). The degree to which the voltage output from the IC varies in direct proportion to the primary current through its half-scale amplitude. Nonlinearity in the output can be attributed to the saturation of the flux concentrator approaching the half-scale current. The following equation is used to derive the linearity: Δ gain % sat ( V { [ IOUT_half-scale amperes V IOUT(Q) ) 2 (V IOUT_quarter-scale amperes V IOUT(Q) ) where gain = the gain variation as a function of temperature changes from 2ºC, % sat = the percentage of saturation of the flux concentrator, which becomes significant as the current being sampled approaches half-scale ±I P, and V IOUT_half-scale amperes = the output voltage (V) when the sampled current approximates half-scale ±I P. Symmetry (E SYM ). The degree to which the absolute voltage output from the IC varies in proportion to either a positive or negative half-scale primary current. The following equation is used to derive symmetry: V IOUT_+ half-scale amperes V IOUT(Q) V IOUT(Q) V IOUT_ half-scale amperes Ratiometry. The device features a ratiometric output. This means that the quiescent voltage output, V IOUTQ, and the magnetic sensitivity, Sens, are proportional to the supply voltage, V CC. { [ The ratiometric change (%) in the quiescent voltage output is defined as: V IOUTQ( V) = V IOUTQ(VCC ) V CC V IOUTQ(V) V % and the ratiometric change (%) in sensitivity is defined as: Sens (VCC Sens ( V Sens ( V = % V CC V Quiescent output voltage (V IOUT(Q) ). The output of the device when the primary current is zero. For bidirectional devices, it nominally remains at V CC 2. Thus, V CC = V translates into V IOUT(QBI) = 2. V. For unidirectional devices, it nominally remains at. V CC. Thus, V CC = V translates into V IOUT(QUNI) =. V. Variation in V IOUT(Q) can be attributed to the resolution of the Allegro linear IC quiescent voltage trim, magnetic hysteresis, and thermal drift. Electrical offset voltage (V OE ). The deviation of the device output from its ideal quiescent value of V CC 2 for bidirectional and. V CC for unidirectional devices, due to nonmagnetic causes. Magnetic offset error (I ERROM ). The magnetic offset is due to the residual magnetism (remnant field) of the core material. The magnetic offset error is highest when the magnetic circuit has been saturated, usually when the device has been subjected to a full-scale or high-current overload condition. The magnetic offset is largely dependent on the material used as a flux concentrator. The larger magnetic offsets are observed at the lower operating temperatures. Total Output Error (E TOT ). The maximum deviation of the actual output from its ideal value, also referred to as accuracy, illustrated graphically in the output voltage versus current chart on the following page. E TOT is divided into four areas: A at 2 C. at the zero current flow at 2 C, without the effects of temperature. A over Δ temperature. at the zero current flow including temperature effects. Half-scale current at 2 C. at the the half-scale current at 2 C, without the effects of temperature. Half-scale current over Δ temperature. at the halfscale current flow including temperature effects.
Definitions of Dynamic Response Characteristics Power-On Time (t PO ). 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, t PO, is defined as the time it takes for the output voltage to settle within ±% of its steady state value under an applied magnetic field, after the power supply has reached its minimum specified operating voltage, V CC (min), as shown in the chart at right. Rise time (t r ). The time interval between a) when the device 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 device, in which ƒ( 3 db) =.3 / 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 Bidirectional Output Voltage versus Sampled Current Total Output Error at A and at Half-Scale Current Oe v r Temp erature Increasing V IOUT (V) Average V IOUT 2 C Only Oe v r Temp erature Transducer Output Rise Time, t r t I P (A) I P(min) 2 C Only +I P (A) Half Scale I P(max) A Propagation delay (t PROP ). 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. 2 C Only Oe v r Temp erature Decreasing V IOUT (V) Increasing V IOUT (V) Oe v r Temp erature I (%) 9 Primary Current Unidirectional Average V IOUT 2 C Only Transducer Output Oe v r Temp erature Propagation Time, t PROP t 2 C Only I P (A) +I P (A) A Full Scale Decreasing V IOUT (V) I P(max) 6
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 modulationdemodulation 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. The anti-aliasing filter prevents aliasing from happening in applications with high frequency signal components which are beyond the user s frequency range of interest. 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 Anti-aliasing Filter Sample and Hold Low-Pass Filter Concept of Chopper Stabilization Technique 7
A ACS78xCB Package CB, -pin package, leadform PFF. R R3 4.±.2. B 3.±.2 4.±.2.±. R2 4 4 º±2 3 2.4 3.±.2.8 3.±. 7.±.2..9 4.4±. Branded Face B PCB Layout Reference View 2 3.38 +.6.3 2.9±.2 º± NNNNNNN TTT - AAA.±. 3.±.2 LLLLLLL YYWW 7.±. C Standard Branding Reference View.±..9±.2 N = Device part number T = Temperature code A = Amperage range L = Lot number Y = Last two digits of year of manufacture W = Week of manufacture = Supplier emblem For Reference Only; not for tooling use (reference DWG-9, DWG-9) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown B C A Dambar removal intrusion Perimeter through-holes recommended Branding scale and appearance at supplier discretion Creepage distance, current terminals to signal pins: 7.2 mm Clearance distance, current terminals to signal pins: 7.2 mm Package mass: 4.63 g typical 8
A ACS78xCB Package CB, -pin package, leadform PSS 4.±.2 3.±.2 4.±.2 4.±. 23.±. 2.7±. NNNNNNN TTT - AAA 3.±. LLLLLLL YYWW 4.4±..±. 2 3.±. Branded Face 3.8±..38 +.6.3 B Standard Branding Reference View N = Device part number T = Temperature code A = Amperage range L = Lot number Y = Last two digits of year of manufacture W = Week of manufacture = Supplier emblem For Reference Only; not for tooling use (reference DWG-9, DWG-9) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown 7.±. A Dambar removal intrusion.±..9±.2 B Branding scale and appearance at supplier discretion Creepage distance, current terminals to signal pins: 7.2 mm Clearance distance, current terminals to signal pins: 7.2 mm Package mass: 4.63 g typical Copyright 28-2, The products described herein are protected by U.S. patents: 6,78,39; and 7,26,3. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to permit improvements in the per for mance, 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 in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, assumes no responsibility for its use; nor for any in fringe ment 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 9