Datasheet AD8417 (Analog Devices) - 10

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AD8417 Data Sheet THEORY OF OPERATION
The AD8417 is a single-supply, zero drift, difference amplifier drift architecture that does not compromise bandwidth, which that uses a unique architecture to accurately amplify small is typically rated at 250 kHz. differential current shunt voltages in the presence of rapidly The reference inputs, VREF1 and VREF2, are tied through 100 kΩ changing common-mode voltages. resistors to the positive input of the main amplifier, which al ows In typical applications, the AD8417 measures current by the output offset to be adjusted anywhere in the output operating amplifying the voltage across a shunt resistor connected to its range. The gain is 1 V/V from the reference pins to the output inputs by a gain of 60 V/V (see Figure 1). when the reference pins are used in parallel. When the pins are The AD8417 design provides excel ent common-mode used to divide the supply, the gain is 0.5 V/V. rejection, even with PWM common-mode inputs that can The AD8417 offers breakthrough performance without change at very fast rates, for example, 1 V/ns. The AD8417 compromising any of the robust application needs typical of contains patented (U.S. Patent 8,624,668 B2) technology to solenoid or motor control. The ability to reject PWM input eliminate the negative effects of such fast changing external common-mode voltages and the zero drift architecture common-mode variations. providing low offset and offset drift al ows the AD8417 to The AD8417 features an input offset drift of less than deliver total accuracy for these demanding applications. 0.4 µV/°C. This performance is achieved through a novel zero Rev. E | Page 10 of 17 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TYPICAL APPLICATION CIRCUIT REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION OUTPUT OFFSET ADJUSTMENT UNIDIRECTIONAL OPERATION Ground Referenced Output Mode VS Referenced Output Mode BIDIRECTIONAL OPERATION EXTERNAL REFERENCED OUTPUT SPLITTING THE SUPPLY SPLITTING AN EXTERNAL REFERENCE APPLICATIONS INFORMATION MOTOR CONTROL 3-Phase Motor Control H-Bridge Motor Control SOLENOID CONTROL High-Side Current Sense with a Low-Side Switch High-Side Current Sense with a High-Side Switch High Rail Current Sensing PINOUT OPTION ENGINEERED FOR FMEA OUTLINE DIMENSIONS ORDERING GUIDE AUTOMOTIVE PRODUCTS