Datasheet AD8206 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | High Common-Mode Voltage, Bidirectional Current Shunt Amplifier |
| Pages / Page | 13 / 9 — Data Sheet. AD8206. THEORY OF OPERATION. –IN. +IN. OUT. REF1. 250mV. … |
| Revision | C |
| File Format / Size | PDF / 363 Kb |
| Document Language | English |
Data Sheet. AD8206. THEORY OF OPERATION. –IN. +IN. OUT. REF1. 250mV. RREF. GND. VREF2
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Data Sheet AD8206 THEORY OF OPERATION
The AD8206 is a single-supply difference amplifier that uses a By attenuating the voltages at Pin 1 and Pin 8, the A1 amplifier unique architecture to accurately amplify small differential current inputs are held within the power supply range, even if Pin 1 and shunt voltages in the presence of rapidly changing common-mode Pin 8 exceed the supply or fall below common (ground). A voltage. It is offered in an 8-lead SOIC package. reference voltage of 250 mV biases the attenuator above ground. In typical applications, the AD8206 is used to measure current This allows the amplifier to operate in the presence of negative by amplifying the voltage across a current shunt placed across common-mode voltages. the inputs. The input network also attenuates normal (differential) mode The gain of the AD8206 is 20 V/V, with an accuracy of 1.2%. voltages. A1 amplifies the attenuated signal by 26. The input This accuracy is guaranteed over the operating temperature range and output of this amplifier are differential to maximize the of −40°C to +125°C. Note, however, that the WH grade version ac common-mode rejection. of the AD8206 is specified for operation from −40°C to +150°C, A2 converts the differential voltage from A1 into a single-ended with the same accuracy of 1.2%. signal and provides further amplification. The gain of this The AD8206 operates with a single supply from 4.5 V to 10 V second stage is 12.86. (absolute maximum = 12.5 V). The supply current is less than The reference inputs, VREF1 and VREF2, are tied through resistors 2 mA. to the positive input of A2, which allows the output offset to be High accuracy trimming of the internal resistors allows the adjusted anywhere in the output operating range. The gain is AD8206 to have a typical common-mode rejection ratio better 1 V/V from the reference pins to the output when the reference than 80 dB from dc to 20 kHz. The minimum common-mode pins are used in parallel. The gain is 0.5 V/V when they are used rejection ratio over the operating temperature is 76 dB. to divide the supply. The output offset can be adjusted from 0.08 V to 4.7 V The ratios of Resistors RA, RB, RC, RD, and RF are trimmed to a (V high level of precision to allow the common-mode rejection S = 5 V) for unidirectional and bidirectional operation. ratio to exceed 80 dB. This is accomplished by laser trimming The AD8206 consists of two amplifiers (A1 and A2), a resistor the resistor ratio matching to better than 0.01%. network, a smal voltage reference, and a bias circuit. See Figure 16 for a simplified schematic diagram (bias circuit not shown). The total gain of 20 is made up of the input attenuation of 1/16.7 multiplied by the first stage gain of 26 and the second The set of input attenuators preceding A1 consist of RA, RB, and stage gain of 12.86. RC, which reduce the common-mode voltage to match the input voltage range of A1. The two attenuators form a balanced bridge The output stage is a Class A with a PNP pull-up transistor and network. When the bridge is balanced, the differential voltage a 300 µA current sink pull-down. created by a common-mode voltage is 0 V at the inputs of A1.
–IN +IN
The input attenuation ratio is 1/16.7. The combined series
R
resistance of R
A RA
A, RB, and RC is approximately 200 kΩ ± 20%.
A1 RB RB RF RF RD RD A2 R V C RC OUT V AD8206 R REF1 E RF 250mV RREF RREF GND VREF2
04953-013 Figure 16. Simplified Schematic Rev. C | Page 9 of 13 Document Outline FEATURES EXCELLENT AC AND DC PERFORMANCE APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION OUTPUT OFFSET ADJUSTMENT UNIDIRECTIONAL OPERATION GROUND REFERENCED OUTPUT V+ REFERENCED OUTPUT BIDIRECTIONAL OPERATION EXTERNAL REFERENCED OUTPUT SPLITTING THE SUPPLY SPLITTING AN EXTERNAL REFERENCE APPLICATIONS INFORMATION HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH OUTLINE DIMENSIONS ORDERING GUIDE AUTOMOTIVE PRODUCTS
Data Sheet AD8206 THEORY OF OPERATION
The AD8206 is a single-supply difference amplifier that uses a By attenuating the voltages at Pin 1 and Pin 8, the A1 amplifier unique architecture to accurately amplify small differential current inputs are held within the power supply range, even if Pin 1 and shunt voltages in the presence of rapidly changing common-mode Pin 8 exceed the supply or fall below common (ground). A voltage. It is offered in an 8-lead SOIC package. reference voltage of 250 mV biases the attenuator above ground. In typical applications, the AD8206 is used to measure current This allows the amplifier to operate in the presence of negative by amplifying the voltage across a current shunt placed across common-mode voltages. the inputs. The input network also attenuates normal (differential) mode The gain of the AD8206 is 20 V/V, with an accuracy of 1.2%. voltages. A1 amplifies the attenuated signal by 26. The input This accuracy is guaranteed over the operating temperature range and output of this amplifier are differential to maximize the of −40°C to +125°C. Note, however, that the WH grade version ac common-mode rejection. of the AD8206 is specified for operation from −40°C to +150°C, A2 converts the differential voltage from A1 into a single-ended with the same accuracy of 1.2%. signal and provides further amplification. The gain of this The AD8206 operates with a single supply from 4.5 V to 10 V second stage is 12.86. (absolute maximum = 12.5 V). The supply current is less than The reference inputs, VREF1 and VREF2, are tied through resistors 2 mA. to the positive input of A2, which allows the output offset to be High accuracy trimming of the internal resistors allows the adjusted anywhere in the output operating range. The gain is AD8206 to have a typical common-mode rejection ratio better 1 V/V from the reference pins to the output when the reference than 80 dB from dc to 20 kHz. The minimum common-mode pins are used in parallel. The gain is 0.5 V/V when they are used rejection ratio over the operating temperature is 76 dB. to divide the supply. The output offset can be adjusted from 0.08 V to 4.7 V The ratios of Resistors RA, RB, RC, RD, and RF are trimmed to a (V high level of precision to allow the common-mode rejection S = 5 V) for unidirectional and bidirectional operation. ratio to exceed 80 dB. This is accomplished by laser trimming The AD8206 consists of two amplifiers (A1 and A2), a resistor the resistor ratio matching to better than 0.01%. network, a smal voltage reference, and a bias circuit. See Figure 16 for a simplified schematic diagram (bias circuit not shown). The total gain of 20 is made up of the input attenuation of 1/16.7 multiplied by the first stage gain of 26 and the second The set of input attenuators preceding A1 consist of RA, RB, and stage gain of 12.86. RC, which reduce the common-mode voltage to match the input voltage range of A1. The two attenuators form a balanced bridge The output stage is a Class A with a PNP pull-up transistor and network. When the bridge is balanced, the differential voltage a 300 µA current sink pull-down. created by a common-mode voltage is 0 V at the inputs of A1.
–IN +IN
The input attenuation ratio is 1/16.7. The combined series
R
resistance of R
A RA
A, RB, and RC is approximately 200 kΩ ± 20%.
A1 RB RB RF RF RD RD A2 R V C RC OUT V AD8206 R REF1 E RF 250mV RREF RREF GND VREF2
04953-013 Figure 16. Simplified Schematic Rev. C | Page 9 of 13 Document Outline FEATURES EXCELLENT AC AND DC PERFORMANCE APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION OUTPUT OFFSET ADJUSTMENT UNIDIRECTIONAL OPERATION GROUND REFERENCED OUTPUT V+ REFERENCED OUTPUT BIDIRECTIONAL OPERATION EXTERNAL REFERENCED OUTPUT SPLITTING THE SUPPLY SPLITTING AN EXTERNAL REFERENCE APPLICATIONS INFORMATION HIGH-SIDE CURRENT SENSE WITH A LOW-SIDE SWITCH HIGH-SIDE CURRENT SENSE WITH A HIGH-SIDE SWITCH OUTLINE DIMENSIONS ORDERING GUIDE AUTOMOTIVE PRODUCTS
