FEATURES Ideal for current shunt applications High common-mode voltage range −2 V to +65 V operating −25 V to +75 V survival Gain = 50 V/V Wide operating temperature range: −40°C to +125°C for Y and W grade −40°C to +150°C for H grade Bidirectional operation Available in 8-lead SOIC Qualified for automotive applications FUNCTIONAL BLOCK DIAGRAM V+ 6 +IN 8 AD8205 NC 4 2 NC = NO CONNECT EXCELLENT AC AND DC PERFORMANCE 5 OUT 7 VREF1 3 VREF2 –IN 1 GND 04315-0-001 Data Sheet Single-Supply 42 V System Difference Amplifier AD8205 Figure 1. 15 µV/°C offset drift 30 ppm/°C gain drift 80 dB CMRR dc to 20 kHz APPLICATIONS High-side current sensing in: Motor controls Transmission controls Diesel injection controls Engine management Suspension controls Vehicle dynamic controls DC-to-dc converters GENERAL DESCRIPTION The AD8205 is a single-supply difference amplifier for amplifying small differential voltages in the presence of large common-mode voltages. The operating input common-mode voltage range extends from −2 V to +65 V. The typical singlesupply voltage is 5 V. The AD8205 is offered in an 8-lead SOIC package and rated for operation from −40°C to +125°C for the Y and W grade models. The H grade version of the AD8205 is rated from −40°C to +150°C. than 15 µV/°C, and gain drift is typically below 30 ppm/°C. The output offset can be adjusted from 0.05 V to 4.8 V with a 5 V supply by using the VREF1 and VREF2 pins. With VREF1 attached to the V+ pin, and VREF2 attached to the GND pin, the output is set at half scale. Attaching both pins to GND causes the output to be unipolar, starting near ground. Attaching both pins to V+ causes the output to be unipolar starting near V+. Other offsets can be obtained by applying an external voltage to the VREF1 and VREF2 pins. Excellent dc performance over temperature keeps errors in the measurement loop to a minimum. Offset drift is typically less Rev. D Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2004–2012 Analog Devices, Inc. All rights reserved. AD8205 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Unidirectional Operation .............................................................9 Excellent AC and DC Performance................................................ 1 Ground Referenced Output .........................................................9 Applications ....................................................................................... 1 V+ Referenced Output .................................................................9 Functional Block Diagram .............................................................. 1 Bidirectional Operation................................................................9 General Description ......................................................................... 1 External Reference Output........................................................ 10 Revision History ............................................................................... 2 Splitting the Supply .................................................................... 10 Specifications..................................................................................... 3 Splitting an External Reference ................................................ 10 Absolute Maximum Ratings............................................................ 4 Applications Information .............................................................. 11 ESD Caution .................................................................................. 4 High-Side Current Sense with a Low-Side Switch ................. 11 Pin Configuration and Function Descriptions ............................. 5 High-Side Current Sense with a High-Side Switch ............... 11 Typical Performance Characteristics ............................................. 6 Outline Dimensions ....................................................................... 12 Theory of Operation ........................................................................ 8 Ordering Guide .......................................................................... 12 Output Offset Adjustment............................................................... 9 Automotive Products ................................................................. 12 REVISION HISTORY 4/12—Rev. C to Rev. D Added H Grade Temperature Range to Table 2 ........................... 4 3/12—Rev. B to Rev. C Added H Grade Models (Throughout) ......................................... 1 Added Unit of V/V to Gain in Features Section........................... 1 Added Radiometric Accuracy Maximum Parameter of 0.503 V/V, Operating Range Maximum Parameter of 5.5 V, and H Grade Specifications (Table 1) .................................................................... 3 Changes to Theory of Operation Section ...................................... 8 Changes to Ordering Guide .......................................................... 12 7/10—Rev. A to Rev. B Changes to Features Section and General Description Section . 1 Delete Die Columns, Table 1 ........................................................... 3 Changes to Table 2 ............................................................................ 4 Changes to Figure 4 and Figure 6 ................................................... 6 Changes to Theory of Operation Section ...................................... 8 Changes to Ordering Guide .......................................................... 12 Added Automotive Products Section .......................................... 12 10/09—Rev. 0 to Rev. A Changes to Output Resistance Parameter, Table 1 ....................... 3 Updated Outline Dimensions ....................................................... 12 Changes to Ordering Guide .......................................................... 12 4/04—Revision 0: Initial Version Rev. D | Page 2 of 12 Data Sheet AD8205 SPECIFICATIONS TA = operating temperature range, VS = 5 V, unless otherwise noted. Table 1. Parameter GAIN Initial Accuracy Accuracy Over Temperature Gain vs. Temperature VOLTAGE OFFSET Offset Voltage (RTI) 1 Over Temperature (RTI)1 Offset Drift INPUT Input Impedance Differential Common Mode Input Voltage Range Common-Mode Rejection OUTPUT Output Voltage Range Output Resistance DYNAMIC RESPONSE Small Signal −3 dB Bandwidth Slew Rate NOISE 0.1 Hz to 10 Hz, RTI Spectral Density, 1 kHz (RTI)1 OFFSET ADJUSTMENT Ratiometric Accuracy 4 Accuracy, RTO Output Offset Adjustment Range VREF Divider Resistor Values POWER SUPPLY Operating Range Quiescent Current Over Temperature Power Supply Rejection Ratio Temperature Range For Specified Performance Test Conditions/Comments Y and W Grade Min Typ Max Min 50 VO ≥ 0.1 V dc, 25°C Specified temperature range 50 ±1 ±1.2 ±30 25°C Specified temperature range Common mode, continuous Differential 2 25°C, f = dc to 20 kHz 3 Operating temperature range, f = dc to 20 kHz3 RL = 25 kΩ 15 400 200 400 200 −2 78 76 65 100 86 80 4.5 VO = 0.1 V dc 4.8 −40 2 3 Rev. D | Page 3 of 12 −2 100 78 76 65 86 80 50 0.5 50 0.5 kHz V/µs 20 0.5 20 0.5 µV p-p µV/√Hz 32 0.05 0.503 ±2 0.497 4.8 40 0.05 24 5.5 2 4.5 4.8 kΩ kΩ V mV dB dB V Ω 32 0.503 ±2 V/V mV/V 4.8 40 V kΩ 5.5 2.2 V mA dB +150 °C 70 +125 RTI is referred to input. Input voltage range = ±50 mV with half-scale offset. Source imbalance < 2 Ω. 4 The offset adjustment is ratiometric to the power supply when VREF1 and VREF2 are used as a divider between the supplies. 1 mV mV µV/°C 2 70 Operating temperature range ±4.5 2 0.497 0.05 24 V/V % % ppm/°C ±2 15 Unit ±1 ±1.2 ±30 ±2 ±4.5 0.05 Divider to supplies Voltage applied to VREF1 and VREF2 in parallel VS = 5 V H Grade Typ Max −40 AD8205 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage Continuous Input Voltage Input Transient Survival Differential Input Survival Reverse Supply Voltage Operating Temperature Range Y and W Grade H Grade Storage Temperature Output Short-Circuit Duration Rating 12.5 V −25 V to +75 V −30 V to +80 V −25 V to +75 V 0.3 V −40°C to +125°C −40°C to +150°C −65 to +150C Indefinite Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION Rev. D | Page 4 of 12 Data Sheet AD8205 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VREF2 3 8 +IN AD8205 7 VREF1 TOP VIEW (Not to Scale) 6 V+ 5 OUT NC 4 NC = NO CONNECT 04315-0-026 –IN 1 GND 2 Figure 3. Pin Configuration 04315-0-002 Table 3. Pin Function Descriptions Figure 2. Metallization Diagram Pin No. 1 2 3 4 5 6 7 8 Mnemonic −IN GND VREF2 NC OUT V+ VREF1 +IN X −206 −447 −432 N/A 444 444 456 203 Y 508 57 −457 N/A −472 −203 434 509 Die size is 1170 µm by 1280 µm. Die thickness is 13 mil. Minimum passivation opening (minimum bond pad size) is 92 µm × 92 µm. Passivation type is 8KA USG (Oxide) + 10KA Oxynitride. Bond pad metal composition is 98.5% Al, 1% Si, and 0.5% Cu. Backside potential is V+. Rev. D | Page 5 of 12 AD8205 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 500 40 400 35 300 30 25 100 GAIN (dB) VOSI (µV) 200 0 –100 TYP. VOSI (SOIC) 20 15 –200 10 –400 –500 –40 –20 0 20 40 60 80 100 120 04315-0-008 04315-0-003 –300 5 0 10 140 100 TEMPERATURE (°C) Figure 4. Typical Offset Drift 1k 10k FREQUENCY (Hz) 100k 1M Figure 7. Typical Small Signal Bandwidth (VOUT = 200 mV p-p) 120 110 100 50mV/DIV 90 CMR (dB) 80 70 60 50 40 30 04315-0-005 04315-0-024 1V/DIV 20 10 0 10 100 1k 10k 100k FREQUENCY (Hz) 1M 40µs/DIV 10M Figure 5. CMR vs. Frequency Figure 8. Rise/Fall Time 12000 100mV/DIV 10000 8000 GAIN ERROR (ppm) 6000 4000 2000 TYP. IN SOIC 0 2V/DIV –2000 –4000 04315-0-007 –8000 –10000 –12000 –40 04315-0-021 –6000 –20 0 20 40 60 80 100 120 2µs/DIV 140 TEMPERATURE (°C) Figure 6. Gain Drift Figure 9. Differential Overload Recovery (Falling) Rev. D | Page 6 of 12 Data Sheet AD8205 50V/DIV 100mV/DIV 50mV/DIV 04315-0-023 04315-0-022 2V/DIV 2µs/DIV 1µs/DIV Figure 10. Differential Overload Recovery (Rising) Figure 12. Common-Mode Response 2V/DIV 04315-0-025 0.01%/DIV 40µs/DIV Figure 11. Settling Time Rev. D | Page 7 of 12 AD8205 Data Sheet THEORY OF OPERATION In typical applications, the AD8205 is used to measure current by amplifying the voltage across a current shunt placed across the inputs. The gain of the AD8205 is 50 V/V, with an accuracy of 1.2%. This accuracy for the Y and W Grade is guaranteed over the operating temperature range of −40°C to +125°C. The H Grade version of the AD8205 is specified for operation from −40°C to +150°C. The input offset is less than 2 mV referred to the input at 25°C, and 4.5 mV maximum referred to the input over the full operating temperature range for the packaged part. The AD8205 operates with a single supply from 4.5 V to 10 V (absolute maximum = 12.5 V). The supply current is less than 2 mA. High accuracy trimming of the internal resistors allows the AD8205 to have a common-mode rejection ratio better than 78 dB from dc to 20 kHz. The output offset can be adjusted from 0.05 V to 4.8 V (V+ = 5 V) for unipolar and bipolar operation. The AD8205 consists of two amplifiers (A1 and A2), a resistor network, small voltage reference, and a bias circuit (not shown), see Figure 13. The set of input attenuators preceding A1 consist of RA, RB, and RC, which reduce the common-mode voltage to match the input voltage range of A1. The two attenuators form a balanced bridge network. When the bridge is balanced, the differential voltage created by a common-mode voltage is 0 V at the inputs of A1. The input attenuation ratio is 1/16.7. The combined series resistance of RA, RB, and RC is approximately 200 kΩ ± 20%. By attenuating the voltages at Pin 1 and Pin 8, the A1 amplifier inputs are held within the power supply range, even if Pin 1 and Pin 8 exceed the supply or fall below common (ground). A reference voltage of 250 mV biases the attenuator above ground. This allows the amplifier to operate in the presence of negative common-mode voltages. The input network also attenuates normal (differential) mode voltages. A1 amplifies the attenuated signal by 26. The input and output of this amplifier are differential to maximize the ac common-mode rejection. A2 converts the differential voltage from A1 into a single-ended signal and provides further amplification. The gain of this second stage is 32.15. The reference inputs, VREF1 and VREF2, are tied through resistors to the positive input of A2, which allows the output offset to be adjusted anywhere in the output operating range. The gain is 1 V/V from the reference pins to the output when the reference pins are used in parallel. The gain is 0.5 V/V when they are used to divide the supply. The ratios of Resistors RA, RB, RC, RD, and RF are trimmed to a high level of precision to allow the common-mode rejection ratio to exceed 80 dB. This is accomplished by laser trimming the resistor ratio matching to better than 0.01%. The total gain of 50 is made up of the input attenuation of 1/16.7 multiplied by the first stage gain of 26 and the second stage gain of 32.15. The output stage is Class A with a PNP pull-up transistor and a 300 µA current sink pull-down. –IN RA +IN RA A1 RB RB RC RC 250mV RF RF RD RD A2 AD8205 RE RF VOUT VREF1 RREF RREF GND VREF2 Figure 13. Simplified Schematic Rev. D | Page 8 of 12 04315-0-012 The AD8205 is a single-supply difference amplifier that uses a unique architecture to accurately amplify small differential current shunt voltages in the presence of rapidly changing common-mode voltages. Data Sheet AD8205 OUTPUT OFFSET ADJUSTMENT UNIDIRECTIONAL OPERATION Unidirectional operation allows the AD8205 to measure currents through a resistive shunt in one direction. The basic modes for unidirectional operation are ground referenced output mode and V+ referenced output mode. V+ REFERENCED OUTPUT This mode is set when both reference pins are tied to the positive supply. It is typically used when the diagnostic scheme requires detection of the amplifier and the wiring before power is applied to the load (see Figure 15). V+ In the case of unidirectional operation, the output could be set at the negative rail (near ground) or at the positive rail (near V+) when the differential input is 0 V. The output moves to the opposite rail when a correct polarity differential input voltage is applied. In this case, full scale is approximately 100 mV. The required polarity of the differential input depends on the output voltage setting. If the output is set at the positive rail, the input polarity needs to be negative to move the output down. If the output is set at ground, the polarity is positive to move the output up. +IN OUT –IN VREF1 AD8205 NC VREF2 GND 04315-0-014 The output of the AD8205 can be adjusted for unidirectional or bidirectional operation. NC = NO CONNECT GROUND REFERENCED OUTPUT Figure 15. V+ Referenced Output When using the AD8205 in this mode, both reference inputs are tied to ground, which causes the output to sit at the negative rail when there are zero differential volts at the input (see Figure 14). Table 5. V+ = 5 V VIN (Referred to −IN) 0V 100 mV V+ +IN VO 4.8 V 0.05 V OUT –IN BIDIRECTIONAL OPERATION Bidirectional operation allows the AD8205 to measure currents through a resistive shunt in two directions. VREF1 AD8205 NC VREF2 04315-0-013 GND NC = NO CONNECT Figure 14. Ground Referenced Output Table 4. V+ = 5 V VIN (Referred to −IN) 0V 100 mV VO 0.05 V 4.8 V In this case, the output is set anywhere within the output range. Typically, it is set at half-scale for equal range in both directions. In some cases, however, it is set at a voltage other than half-scale when the bidirectional current is nonsymmetrical. Table 6. V+ = 5 V, VO = 2.5 with VIN = 0 V VIN (Referred to −IN) +40 mV −40 mV VO 4.5 V 0.5 V Adjusting the output is accomplished by applying voltage(s) to the reference inputs. VREF1 and VREF2 are tied to internal resistors that connect to an internal offset node. There is no operational difference between the pins. Rev. D | Page 9 of 12 AD8205 Data Sheet EXTERNAL REFERENCE OUTPUT Tying both pins together and to a reference produces an output at the reference voltage when there is no differential input (see Figure 16). The output moves down from the reference voltage when the input is negative relative to the −IN pin and up when the input is positive relative to the −IN pin. V+ +IN OUT –IN VREF1 AD8205 V+ +IN OUT –IN NC VREF2 VREF1 AD8205 04315-0-016 GND NC = NO CONNECT 2.5V VOLTAGE REFERENCE Figure 17. Split Supply NC SPLITTING AN EXTERNAL REFERENCE VREF2 NC = NO CONNECT 04315-0-015 GND Figure 16. External Reference Output In this case, an external reference is divided by 2 with an accuracy of approximately 0.5% by connecting one VREF pin to ground and the other VREF pin to the reference (see Figure 18). SPLITTING THE SUPPLY V+ +IN OUT –IN VREF1 AD8205 5V NC VREF2 GND NC = NO CONNECT Figure 18. Split External Reference Rev. D | Page 10 of 12 VOLTAGE REFERENCE 04315-0-017 By tying one reference pin to V+ and the other to the ground pin, the output is set at half of the supply when there is no differential input (see Figure 17). The benefit is that no external reference is required to offset the output for bidirectional current measurement. This creates a midscale offset that is ratiometric to the supply, which means that if the supply increases or decreases, the output remains at half the supply. For example, if the supply is 5.0 V, the output is at half scale or 2.5 V. If the supply increases by 10% (to 5.5 V), the output goes to 2.75 V. Data Sheet AD8205 APPLICATIONS INFORMATION A typical application for the AD8205 is high-side measurement of a current through a solenoid for PWM control of the solenoid opening. Typical applications include hydraulic transmission control and diesel injection control. Two typical circuit configurations are used for this type of application. When using a high-side switch, the battery voltage is connected to the load when the switch is closed, causing the commonmode voltage to increase to the battery voltage. In this case, when the switch is opened, the voltage reversal across the inductive load causes the common-mode voltage to be held one diode drop below ground by the clamp diode. 5V HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH SWITCH In this case, the PWM control switch is ground referenced. An inductive load (solenoid) is tied to a power supply. A resistive shunt is placed between the switch and the load (see Figure 19). An advantage of placing the shunt on the high side is that the entire current, including the re-circulation current, can be measured since the shunt remains in the loop when the switch is off. In addition, diagnostics can be enhanced because shorts to ground can be detected with the shunt on the high side. In this circuit configuration, when the switch is closed, the common-mode voltage moves down to near the negative rail. When the switch is opened, the voltage reversal across the inductive load causes the common-mode voltage to be held one diode drop above the battery by the clamp diode. 5V 42V BATTERY INDUCTIVE LOAD +IN VREF1 +VS OUT AD8205 SHUNT –IN OUT AD8205 SHUNT –IN GND VREF2 NC CLAMP DIODE 04315-0-019 INDUCTIVE LOAD NC = NO CONNECT Figure 20. High-Side Switch Another typical application for the AD8205 is as part of the control loop in H-bridge motor control. In this case, the AD8205 is placed in the middle of the H-bridge (see Figure 21) so that it can accurately measure current in both directions by using the shunt available at the motor. This is a better solution than a ground referenced op amp because ground is not typically a stable reference voltage in this type of application. This instability in the ground reference causes the measurements that could be made with a simple ground referenced op amp to be inaccurate. The AD8205 measures current in both directions as the H-bridge switches and the motor changes direction. The output of the AD8205 is configured in an external reference bidirectional mode, see the Output Offset Adjustment section. GND VREF2 NC 04315-0-018 SWITCH NC = NO CONNECT +IN VREF1 +VS CONTROLLER 5V Figure 19. Low-Side Switch HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH MOTOR +IN VREF1 +VS OUT AD8205 This configuration minimizes the possibility of unexpected solenoid activation and excessive corrosion (see Figure 20). In this case, both the switch and the shunt are on the high side. When the switch is off, this removes the battery from the load, which prevents damage from potential shorts to ground, while still allowing the recirculating current to be measured and providing for diagnostics. Removing the power supply from the load for the majority of the time minimizes the corrosive effects that could be caused by the differential voltage between the load and ground. Rev. D | Page 11 of 12 SHUNT –IN GND VREF2 NC 5V 2.5V NC = NO CONNECT Figure 21. Motor Control Application 04315-0-020 CLAMP DIODE 42V BATTERY AD8205 Data Sheet OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 1 5 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE 6.20 (0.2441) 5.80 (0.2284) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. 012407-A 8 4.00 (0.1574) 3.80 (0.1497) Figure 22. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) ORDERING GUIDE Model1, 2 AD8205YRZ AD8205YRZ-RL AD8205YRZ-R7 AD8205WYRZ AD8205WYRZ-RL AD8205WYRZ-R7 AD8205WHRZ AD8205WHRZ-RL 1 2 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +125°C −40°C to +150°C −40°C to +150°C Package Description 8-Lead SOIC_N 8-Lead SOIC_N, 13” Tape and Reel 8-Lead SOIC_N, 7” Tape and Reel 8-Lead SOIC_N 8-Lead SOIC_N, 13” Tape and Reel 8-Lead SOIC_N, 7” Tape and Reel 8-Lead SOIC_N 8-Lead SOIC_N, 13” Tape and Reel Package Option R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 Z = RoHS Compliant Part. W = Qualified for Automotive Applications. AUTOMOTIVE PRODUCTS The AD8205WYRZ and AD8205WHRZ models are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these models. ©2004–2012 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04315-0-4/12(D) Rev. D | Page 12 of 12