The AD7691 is an 18-bit, charge redistribution, successive approximation, analog-to-digital converter (ADC) that operates from a single power supply, VDD, between 2.3 V and 5 V. It contains a low power, high speed, 18-bit sampling ADC with no missing codes, an internal conversion clock, and a versatile serial interface port. On the CNV rising edge, it samples the voltage difference between the IN+ and IN− pins. The voltages on these pins usually swing in opposite phase between 0 V and REF. The reference voltage, REF, is applied externally and can be set up to the supply voltage.
Its power scales linearly with throughput.
The SPI-compatible serial interface also features the ability, using the SDI input, to daisy-chain several ADCs on a single 3-wire bus and provides an optional busy indicator. It is compatible with 1.8 V, 2.5 V, 3 V, or 5 V logic, using the separate VIO supply.
The AD7691 is housed in a 10-lead MSOP or a 10-lead QFN (LFCSP) with operation specified from −40°C to +85°C.
|Title||Content Type||File Type|
|AD7691: 18-Bit, 1.5 LSB INL, 250 kSPS PulSAR Differential ADC in MSOP/QFN Data Sheet (Rev C, 03/2012) (pdf, 892 kB)||Data Sheets|
|Tested ADC Driver to PulSAR ADC||Application Notes||HTML|
|AN-1141: Powering a Dual Supply Precision ADC with Switching Regulators (pdf, 640 kB)||Application Notes|
AN-931: Understanding PulSAR ADC Support Circuitry
(pdf, 299 kB)
This application note discusses in general the pitfalls that occur regularly when using SAR ADCs and, more importantly, how to easily prevent them.
|AN-932: Power Supply Sequencing (pdf, 95 kB)||Application Notes|
|AN-877: Interfacing to High Speed ADCs via SPI (pdf, 1594 kB)||Application Notes|
|AN-935: Designing an ADC Transformer-Coupled Front End (pdf, 363 kB)||Application Notes|
|AN-742: Frequency Domain Response of Switched-Capacitor ADCs (pdf, 401 kB)||Application Notes|
|CN-0261: Optimizing AC Performance in an 18-bit, 250 kSPS, PulSAR Measurement Circuit (pdf, 327 kB)||Circuit Note|
|The Data Conversion Handbook||Design Handbooks||HTML|
|MT-031: Grounding Data Converters and Solving the Mystery of (pdf, 144 kB)||Tutorials|
|MT-002: What the Nyquist Criterion Means to Your Sampled Data System Design (pdf, 152 kB)||Tutorials|
|MT-001: Taking the Mystery out of the Infamous Formula, "SNR=6.02N + 1.76dB," and Why You Should Care (pdf, 94 kB)||Tutorials|
|MT-074: Differential Drivers for Precision ADCs (pdf, 249 kB)||Tutorials|
|UG-340: Evaluation Board for the 10-Lead Family 14-/16-/18-Bit PulSAR ADCs (pdf, 4636 kB)||User Guides|
Voltage Reference Design for Precision Successive-Approximation ADCs
(Analog Dialogue, Volume 47 – June 2013)
|Front-End Amplifier and RC Filter Design for a Precision SAR Analog-to-Digital Converter||Technical Articles||HTML|
|MS-2210: Designing Power Supplies for High Speed ADC (pdf, 327 kB)||Technical Articles|
|MS-2022: Seven Steps to Successful Analog-to-Digital Signal Conversion (Noise Calculation for Proper Signal Conditioning) (pdf, 277 kB)||Technical Articles|
|MS-2124: Understanding AC Behaviors of High Speed ADCs (pdf, 276 kB)||Technical Articles|
Nine Often Overlooked ADC Specifications
(pdf, 445 kB)
Analog-to-digital converters (ADCs) have many specifications; some are more important for a given application than others. Understanding these specifications and controlling external devices affecting the ADC will lead to better performance.
|Reduce Noise and Power Levels with Precision Data Acquisition Solution||Technical Articles||HTML|
Dimensions in Data Conversion: An Evolving Story
(Electronic Products, April 2006)
Analog Claims 18-bit ADCs Are the Smallest
18-bit A/D Packs Speed & Precision into MSOP
18-bit ADC Features MSOP Package
(Portable Design, 10/31/2005)
SAR ADC & Driver Quick-Match Guide
(pdf, 251 kB)
Find drivers for ADI's most popular single-ended and differential SAR ADCs based on your specific application conditions.
|Product Selection Guide|
|When high performance and low power make the design, ADI converters make the difference.||Overview||HTML|
High Speed, High Accuracy 14-Bit, 16-Bit, and 18-Bit PulSAR ADCs
(pdf, 3826 kB)
A PulSAR Family Brochure (6/2006)
|RAQs index||Rarely Asked Questions||HTML|
|Glossary of EE Terms||Glossary||HTML|
|Title||Content Type||File Type|
|AD7685 IBIS Models||IBIS Models||HTML|
|BeMicro FPGA Project for AD7691 with Nios driver||FPGA HDL||HTML|
|AD7691 FMC-SDP Interposer & Evaluation Board / Xilinx KC705 Reference Design||FPGA HDL||HTML|
Recommended Digital Isolators for the AD7691
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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.