High Speed, 0.1 V/C Offset Drift, Fully Differential ADC Driver Data Sheet ADA4945-1 FEATURES FUNCTIONAL BLOCK DIAGRAM ADA4945-1 Broad power supply range: 3 V to 10 V Wide input common-mode voltage range: V to +V 1.3 V S S Rail-to-rail output Fully specified dual power mode operation 4 mA full power mode (145 MHz) FB 1 12 DISABLE 1.4 mA low power mode (80 MHz) +IN 2 11 OUT Full power mode IN 3 10 +OUT Low harmonic distortion 49 V +FB OCM 133 dBc HD2 and 140 dBc HD3 at 1 kHz 133 dBc HD2 and 116 dBc HD3 at 100 kHz Fast settling time 18-bit: 100 ns 16-bit: 50 ns NOTES Input voltage noise: 1.8 nV/Hz, f = 100 kHz 1. CONNECT THE EXPOSED PAD TO V . S 115 V maximum offset voltage from 40C to +125C Figure 1. Adjustable output clamps for ADC input protection APPLICATIONS Low power -, PulSAR, and SAR ADC drivers Single-ended to differential converters Differential buffers Medical imaging Process control Portable electronics GENERAL DESCRIPTION The ADA4945-1 is a low noise, low distortion, fully differential provides exceptional output balance, as well as suppression of amplifier with two selectable power modes. The device operates even order harmonic distortion products. over a broad power supply range of 3 V to 10 V. The low dc With the ADA4945-1, differential gain configurations are offset, dc offset drift, and excellent dynamic performance of the achieved with a simple external feedback network of four ADA4945-1 makes it well suited for a variety of data resistors determining the closed-loop gain of the amplifier. acquisition and signal processing applications. The device is an The ADA4945-1 is fabricated using Analog Devices, Inc., ideal choice for driving high resolution, high performance proprietary, silicon germanium (SiGe), complementary bipolar successive approximation register (SAR) and - analog-to-digital process, enabling the device to achieve low levels of distortion converters (ADCs) on 4 mA of quiescent current (full power with an input voltage noise of only 1.8 nV/Hz (full power mode). mode). The device can also be selected to operate on 1.4 mA of The ADA4945-1 is available in a RoHS-compliant, 3 mm 3 mm, quiescent current (low power mode) to scale the power 16-lead LFCSP. The ADA4945-1 is specified to operate from consumption to the desired performance necessary for an ADC 40C to +125C. drive application. The adjustable common-mode voltage allows the ADA4945-1 to match the input common-mode voltage of multiple ADCs. The internal common-mode feedback loop Rev. 0 Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 2019 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. MODE 5 16 D GND +V 6 15 V S S +V 7 14 V S S 8 13 V +V CLAMP CLAMP 16932-001ADA4945-1 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Fully Differential and Common-Mode Signal Paths ............. 35 Applications ....................................................................................... 1 Output Voltage Clamp ............................................................... 36 Functional Block Diagram .............................................................. 1 Power Modes ............................................................................... 36 General Description ......................................................................... 1 Applications Information .............................................................. 37 Revision History ............................................................................... 2 Analyzing an Application Circuit ............................................ 37 Specifications ..................................................................................... 3 Setting the Closed-Loop Gain .................................................. 37 Supply Voltage (V ) = 10 V ......................................................... 3 Estimating the Output Noise Voltage ...................................... 37 S V = 5 V .......................................................................................... 7 Impact of Mismatches in the Feedback Networks ................. 38 S VS = 3 V ........................................................................................ 11 Calculating the Input Impedance of an Application Circuit ..... 38 Absolute Maximum Ratings .......................................................... 15 Input Common-Mode Voltage Range ..................................... 40 Thermal Resistance .................................................................... 15 Input and Output Capacitive AC Coupling ............................ 40 Maximum Power Dissipation ................................................... 15 Setting the Output Common-Mode Voltage .......................... 40 ESD Caution ................................................................................ 15 Disable Pin .................................................................................. 40 Pin Configuration and Function Descriptions ........................... 16 Driving a Capacitive Load ......................................................... 40 Typical Performance Characteristics ........................................... 17 Output Clamps ........................................................................... 41 Full Power Mode .......................................................................... 17 Driving a High Precision ADC ................................................ 42 Low Power Mode ........................................................................ 25 Layout, Grounding, and Bypassing .............................................. 43 Test Circuits ..................................................................................... 33 Outline Dimensions ....................................................................... 44 Terminology .................................................................................... 34 Ordering Guide .......................................................................... 44 Theory of Operation ...................................................................... 35 REVISION HISTORY 4/2019Revision 0: Initial Version Rev. 0 Page 2 of 44