link to page 1 link to page 1 link to page 1 link to page 1 link to page 3 link to page 4 link to page 4 link to page 6 link to page 9 link to page 9 link to page 9 link to page 10 link to page 11 link to page 21 link to page 21 link to page 21 link to page 22 link to page 22 link to page 22 link to page 23 link to page 23 link to page 24 link to page 24 link to page 26 link to page 26 link to page 27 link to page 28 link to page 28 AD8421Data SheetTABLE OF CONTENTS Features .. 1 Gain Selection... 20 Applications... 1 Reference Terminal .. 21 Pin Connection Diagram .. 1 Input Voltage Range... 21 General Description ... 1 Layout .. 21 Revision History ... 2 Input Bias Current Return Path ... 22 Specifications... 3 Input Voltages Beyond the Supply Rails.. 22 AR and BR Grades.. 3 Radio Frequency Interference (RFI).. 23 ARM and BRM Grades.. 5 Calculating the Noise of the Input Stage... 23 Absolute Maximum Ratings.. 8 Applications Information .. 25 Thermal Resistance .. 8 Differential Output Configuration .. 25 ESD Caution.. 8 Driving an ADC ... 26 Pin Configuration and Function Descriptions... 9 Outline Dimensions ... 27 Typical Performance Characteristics ... 10 Ordering Guide .. 27 Theory of Operation .. 20 Architecture... 20 REVISION HISTORY5/12—Revision 0: Initial Version Rev. 0 | Page 2 of 28 Document Outline FEATURES APPLICATIONS PIN CONNECTION DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS AR AND BR GRADES ARM AND BRM GRADES ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION ARCHITECTURE GAIN SELECTION RG Power Dissipation REFERENCE TERMINAL INPUT VOLTAGE RANGE LAYOUT Common-Mode Rejection Ratio over Frequency Power Supplies and Grounding Reference Pin INPUT BIAS CURRENT RETURN PATH INPUT VOLTAGES BEYOND THE SUPPLY RAILS Input Voltages Beyond the Maximum Ratings RADIO FREQUENCY INTERFERENCE (RFI) CALCULATING THE NOISE OF THE INPUT STAGE Source Resistance Noise Voltage Noise of the Instrumentation Amplifier Current Noise of the Instrumentation Amplifier Total Noise Density Calculation APPLICATIONS INFORMATION DIFFERENTIAL OUTPUT CONFIGURATION DRIVING AN ADC OUTLINE DIMENSIONS ORDERING GUIDE