250 kSPS, 6-Channel, Simultaneous Sampling, Bipolar 16-Bit ADC Data Sheet AD7656A FEATURES FUNCTIONAL BLOCK DIAGRAM V CONVST A CONVST B CONVST C AV DV DD CC CC 6 independent analog-to-digital converters (ADCs) True bipolar analog inputs CS Pin-/software-selectable ranges: 10 V or 5 V CLK REF SER/PAR/SEL CONTROL OSC LOGIC V Fast throughput rate: 250 kSPS DRIVE STBY iCMOS process technology BUF OUTPUT Low power: 140 mW at 250 kSPS with 5 V supplies DB8/DOUT A 16-BIT SAR DRIVERS V1 T/H Wide input bandwidth SCLK 86.5 dB SNR at 50 kHz input frequency V2 T/H 16-BIT SAR On-chip reference and reference buffers OUTPUT DB9/DOUT B BUF DRIVERS Parallel, serial, and daisy-chain interface modes V3 T/H 16-BIT SAR OUTPUT High speed serial interface DRIVERS DB10/DOUT C Serial peripheral interface (SPI)/QSPI/MICROWIRE/DSP T/H V4 16-BIT SAR DATA/ compatible OUTPUT CONTROL DRIVERS BUF LINES Power-down mode: 100 mW maximum V5 T/H 16-BIT SAR 64-lead LQFP RD Improved power supply sequencing (PSS) robustness WR/REF EN/DIS V6 T/H 16-BIT SAR AD7656A APPLICATIONS V AGND DGND SS Power line monitoring systems Figure 1. Instrumentation and control systems Multi-axis positioning systems GENERAL DESCRIPTION 1 The AD7656A contains six 16-bit, fast, low power, successive The conversion process and data acquisition are controlled approximation analog-to-digital converters (ADCs) all in the using CONVST x signals and an internal oscillator. Three one package that is designed on the iCMOS process (industrial CONVST x pins (CONVST A, CONVST B, and CONVST C) CMOS). iCMOS is a process combining high voltage silicon allow independent, simultaneous sampling of the three ADC with submicron CMOS and complementary bipolar technologies. pairs. The AD7656A has a high speed parallel and serial interface, It enables the development of a wide range of high performance allowing the device to interface with microprocessors or digital signal processors (DSPs). In serial interface mode, the AD7656A analog ICs, capable of 33 V operation in a footprint that no has a daisy-chain feature that allows multiple ADCs to connect previous generation of high voltage devices could achieve. Unlike analog ICs using conventional CMOS processes, iCMOS to a single serial interface. The AD7656A can accommodate components can accept bipolar input signals while providing true bipolar input signals in the 4 VREF range and 2 VREF increased performance, which dramatically reduces power range. The AD7656A also contains an on-chip 2.5 V reference. consumption and package size. Multifunction pin names may be referenced by their relevant The AD7656A features throughput rates of up to 250 kSPS. It function only. contains wide bandwidth (12 MHz), track-and-hold amplifiers PRODUCT HIGHLIGHTS that can handle input frequencies up to 12 MHz. 1. Six 16-bit, 250 kSPS ADCs on board. 2. Six true bipolar, high impedance analog inputs. 3. Parallel and high speed serial interfaces. 1 Protected by U.S. Patent No. 6,731,232. 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 2013 Analog Devices, Inc. All rights reserved. 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. Technical Support www.analog.com 11127-001AD7656A Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation ...................................................................... 15 Applications ....................................................................................... 1 Converter Details ....................................................................... 15 Functional Block Diagram .............................................................. 1 ADC Transfer Function ............................................................. 16 General Description ......................................................................... 1 Reference Section ....................................................................... 16 Product Highlights ........................................................................... 1 Typical Connection Diagram ................................................... 16 Revision History ............................................................................... 2 Driving the Analog Inputs ........................................................ 17 Specifications ..................................................................................... 3 Interface Section ......................................................................... 17 Timing Specifications .................................................................. 5 Software Selection of ADCs ...................................................... 19 Absolute Maximum Ratings ............................................................ 6 Serial Read Operation ................................................................ 21 Power Supply Sequencing ........................................................... 6 Daisy-Chain Mode (DCEN = 1, SER/PAR/SEL = 1) ............. 21 Thermal Resistance ...................................................................... 6 Application Hints ........................................................................... 24 ESD Caution .................................................................................. 6 Layout .......................................................................................... 24 Pin Configuration and Function Descriptions ............................. 7 Outline Dimensions ....................................................................... 25 Typical Performance Characteristics ........................................... 10 Ordering Guide .......................................................................... 25 Terminology .................................................................................... 13 REVISION HISTORY 12/13Revision 0: Initial Version Rev. 0 Page 2 of 28