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AD7691:  18-Bit, 1.5 LSB INL, 250 kSPS PulSAR® Differential ADC in MSOP/QFN

Product Details


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.

Applications

  • Battery-powered equipment
  • Data acquisitions
  • Seismic data acquisition systems
  • Instrumentation
  • Medical instruments

FEATURES and BENEFITS

  • 18-bit resolution with no missing codes
  • Throughput: 250 kSPS
  • INL: ±0.75 LSB typical, ±1.5 LSB maximum (±6 ppm of FSR)
  • Dynamic range: 102 dB typical @ 250 kSPS
  • Oversampled dynamic range: 125 dB @1 kSPS
  • Noise-free code resolution: 20 bits @ 1 kSPS
  • Effective resolution: 22.7 bits @ 1 kSPS
  • SINAD: 101.5 dB typical @ 1 kHz
  • THD: −125 dB typical @ 1 kHz
  • True differential analog input range: ±VREF 0 V to VREF with VREF up to VDD on both inputs
  • No pipeline delay
  • Single-supply 2.3 V to 5 V operation with 1.8 V/2.5 V/3 V/5 V logic interface
  • Serial interface SPI-/QSPI™-/MICROWIRE™-/DSP-compatible
  • Ability to daisy-chain multiple ADCs
  • Optional busy indicator feature
  • Power dissipation
    1.35 mW @ 2.5 V/100 kSPS, 4 mW @ 5 V/100 kSPS
    1.4 μW @ 2.5 V/100 SPS
  • Standby current: 1 nA
  • 10-lead packages: MSOP (MSOP-8 size) and 3 mm × 3 mm QFN (LFCSP) (SOT-23 size)
  • Pin-for-pin compatible with the18-bit AD7690 and 16-bit AD7693, AD7688, and AD7687

Functional Block Diagram for AD7691

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High Resolution - Single Channel Unipolar/Bipolar 14/16/18-Bit PulSAR ADCs

Documentation

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 PDF
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 PDF
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.
Application Notes PDF
AN-932: Power Supply Sequencing  (pdf, 95 kB) Application Notes PDF
AN-877: Interfacing to High Speed ADCs via SPI  (pdf, 1594 kB) Application Notes PDF
AN-935: Designing an ADC Transformer-Coupled Front End  (pdf, 363 kB) Application Notes PDF
AN-742: Frequency Domain Response of Switched-Capacitor ADCs  (pdf, 401 kB) Application Notes PDF
CN-0261: Optimizing AC Performance in an 18-bit, 250 kSPS, PulSAR Measurement Circuit  (pdf, 327 kB) Circuit Note PDF
The Data Conversion Handbook Design Handbooks HTML
MT-031: Grounding Data Converters and Solving the Mystery of  (pdf, 144 kB) Tutorials PDF
MT-002: What the Nyquist Criterion Means to Your Sampled Data System Design  (pdf, 152 kB) Tutorials PDF
MT-001: Taking the Mystery out of the Infamous Formula, "SNR=6.02N + 1.76dB," and Why You Should Care  (pdf, 94 kB) Tutorials PDF
MT-074: Differential Drivers for Precision ADCs  (pdf, 249 kB) Tutorials PDF
UG-340: Evaluation Board for the 10-Lead Family 14-/16-/18-Bit PulSAR ADCs  (pdf, 4636 kB) User Guides PDF
Voltage Reference Design for Precision Successive-Approximation ADCs
(Analog Dialogue, Volume 47 – June 2013)
Analog Dialogue HTML
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 PDF
MS-2022: Seven Steps to Successful Analog-to-Digital Signal Conversion (Noise Calculation for Proper Signal Conditioning)  (pdf, 277 kB) Technical Articles PDF
MS-2124: Understanding AC Behaviors of High Speed ADCs  (pdf, 276 kB) Technical Articles PDF
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.
Technical Articles PDF
Reduce Noise and Power Levels with Precision Data Acquisition Solution Technical Articles HTML
Dimensions in Data Conversion: An Evolving Story
(Electronic Products, April 2006)
Product Reviews HTML
Analog Claims 18-bit ADCs Are the Smallest
(EDN, 11/1/2005)
Product Reviews HTML
18-bit A/D Packs Speed & Precision into MSOP
(eeProductCenter, 11/2/2005)
Product Reviews HTML
18-bit ADC Features MSOP Package
(Portable Design, 10/31/2005)
Product Reviews HTML
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 PDF
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)
Overview PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Design Tools,Models,Drivers & Software

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

Evaluation Kits & Symbols & Footprints

Evaluation Boards & KitsView the Evaluation Boards and Kits page for documentation and purchasing

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

Product Recommendations & Reference Designs

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Companion Products

Suggested Companion Products


Recommended Driver Amplifiers for the AD7691 Recommended External Voltage References for the AD7691
  • For low drift, low noise and high current output applications, we recommend the ADR435 reference family.
  • For low drift, low noise and low dropout, we recommend the ADR445 reference family.
  • For low drift, low noise, low power, we recommend the ADR4550 reference family.
  • For driving the voltage reference input, we recommend the AD8031 or the AD8655 buffer amplifiers.

Recommended Digital Isolators for the AD7691

  • For SPI Interface, lowest power, 2.5 kVrms isolation, we recommend the ADuM1401.
  • For SPI Interface, enhanced system-level ESD performance, 2.5 kVrms isolation, we recommend the ADuM3401.
  • For SPI Interface, low power, 5.0 kVrms isolation, we recommend the ADuM4401.
  • For SPI Interface, smallest package, low voltage I/O (1.8 V to 5.5 V), we recommend the ADuM3481.
Recommended Power Solutions
  • For selecting voltage regulator products, use ADIsimPower.

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Price, packaging, availability

AD7691 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD7691BCPZRL Status: Last Time Buy 10 ld LFCSP (3x3mm) 10 Ind Reel, 5000 - $14.67 Y  Material Info PDN Purchase
AD7691BCPZRL7 Status: Production 10 ld LFCSP (3x3mm) 10 Ind Reel, 1500 - $14.67 Y  Material Info Notify Me Purchase Sample
AD7691BRMZ Status: Production 10 ld MSOP 10 Ind Tube, 50 $16.23 $14.67 Y  Material Info PCN Purchase Sample
AD7691BRMZ-RL7 Status: Production 10 ld MSOP 10 Ind Reel, 1000 - $14.67 Y  Material Info PCN Purchase
Price Table Help

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.

AD7691 Evaluation Kit
Model Description Price RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
EVAL-AD7691-PMDZ Status: Pre-Release Evaluation Board PMOD compatible form factor $27.00 Yes - Contact ADI
EVAL-AD7691SDZ Status: Production Evaluation Board SDP Interface $99.00 Yes -
EVAL-SDP-CB1Z Status: Production Evaluation Controller Board SDP $99.00 Yes -
SDP-PMD-IB1Z Status: Production Evaluation Interposer Board PMOD to SDP w/ Power Supply $55.00 Yes -

Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.

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