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AD7711:  CMOS, 24-Bit Sigma-Delta, Signal Conditioning ADC with Matched RTD Excitation Currents

Product Details


The AD7711 is a complete analog front end for low frequency measurement applications. The device accepts low level signals directly from a transducer and outputs a serial digital word. It employs a sigma-delta conversion technique to realize up to 24 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via the on-chip control register allowing adjustment of the filter cutoff and settling time.

The part features one differential analog input and one single ended analog input as well as a differential reference input. Normally, one of the input channels will be used as the main channel with the second channel used as an auxiliary input to periodically measure a second voltage. It can be operated from a single supply (by tying the VSS pin to AGND) provided that the input signals on the analog inputs are more positive than -30 mV. By taking the VSS pin negative, the part can convert signals down to -VREF on its inputs. The part provides two current sources that can be used to provide excitation in three-wire and four-wire RTD configurations. The AD7711 thus performs all signal conditioning and conversion for a single or dual channel system.

The AD7711 is ideal for use in smart, microcontroller based systems. Gain settings, signal polarity, input channel selection and RTD current control can be configured in software using the bidirectional serial port. The AD7711 contains self-measurement calibration, system calibration and background calibration options and also allows the user to read and write the on-chip calibration registers.

CMOS construction ensures low power dissipation, and a software programmable power-down mode reduces the standby power consumption to only 7 mW typical. The part is available in a 24-pin, 0.3 inch wide, plastic and hermetic dual-in-line package (DIP) as well as a 24-lead small outline (SOIC) package.

FEATURES and BENEFITS

  • Charge-Balancing ADC
    - 24 Bits, No Missing Codes
    - ±0.0015% Nonlinearity
  • 2-Channel Programmable Gain Front End
    - Gains from 1 to 128
    - 1 Differential Input
    - 1 Single-Ended Input
  • Low-Pass Filter with Programmable Filter Cutoffs
  • Ability to Read/Write Calibration Coefficients
  • RTD Excitation Current Sources
  • Bidirectional Microcontroller Serial Interface
  • Internal/External Reference Option
  • Single- or Dual-Supply Operation
  • Low Power (25 mW typ) with Power-Down Mode (7 mW typ)

Functional Block Diagram for AD7711

Documentation

Title Content Type File Type
AD7711: LC2MOS Signal Conditioning ADC with RTD Excitation Currents Data Sheet  (Rev G, 03/2004) (pdf, 1129 kB) Data Sheets 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-311: How to Reliably Protect CMOS Circuits Against Power Supply Overvoltaging  (pdf, 217 kB) Application Notes PDF
AN-607: Selecting a Low Bandwidth (<15 kSPS) Sigma-Delta ADC  (pdf, 222 kB) Application Notes PDF
AN-615: Peak-to-Peak Resolution Versus Effective Resolution  (pdf, 70 kB)
This application note describes effective resolution and peak-to-peak resolution and highlights the difference between these two specifications.
Application Notes PDF
AN-397: Electrically Induced Damage to Standard Linear Integrated Circuits:  (pdf, 149 kB)
The Most Common Causes and the Associated Fixes to Prevent Reoccurrence
Application Notes PDF
AN-202: An IC Amplifier User’s Guide to Decoupling, Grounding, and Making Things Go Right for a Change  (pdf, 76 kB) Application Notes PDF
AN-389: Using Sigma-Delta Converters-Part 2  (pdf, 590 kB)
When to Use/How to Use Sigma-Delta ADCs; Continuation of Part 1 Discussion.
Application Notes PDF
AN-388: Using Sigma-Delta Converters-Part 1  (pdf, 590 kB)
When to Use/How to Use Sigma-Delta ADCs
Application Notes PDF
AN-283: Sigma-Delta ADCs and DACs  (pdf, 1699 kB)
Overview of Sigma-Delta Concepts: Oversampling, Noise Shaping Using the Sigma-Delta Modulator, Digital Filtering and Decimation.
Application Notes PDF
AN-366: Evaluation Board for the AD7711 24-Bit Sigma-Delta ADC  (pdf, 454 kB) Application Notes PDF
AN-406: 06: Using the AD771X Family of 24-Bit Sigma-Delta A/D Converters  (pdf, 187 kB) Application Notes PDF
AN-553: Adjusting the Calibration Coefficients on the AD771X Family of ADCs  (pdf, 221 kB) Application Notes PDF
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
Delta-Sigma Rocks RF, As ADC Designers Jump On Jitter
(Electronic Design, 1/12/06)
Technical Articles HTML
Circuit Suggestions Using Features and Functionality of New Sigma-Delta ADCs Technical Articles HTML
Designing and Applying Remote Field Instruments
by Albert O' Grady and Jim Ryan, Analog Devices B.V.
...Good things can come in small packages because of on-chip capabilities
(Control Engineering, September 1998)
Technical Articles HTML
Transducer/Sensor Excitation and Measurement Techniques
(Analog Dialogue, Vol. 34, No. 5, August-September, 2000)
Analog Dialogue HTML
Ask the Applications Engineer-27: What problems am I most likely to run into when instrumenting an industrial system?
(Analog Dialogue, Vol. 33, No. 2, February, 1999)
Analog Dialogue HTML
Space Qualified Parts List  (pdf, 93 kB)
This document lists 67 (240+) space level products that are available from Analog Devices. Many of the products listed are state-of-the-art data conversion and signal processing products that were previously only available as commercial or military Class B products. Through our Space Products Group and MIL-PRF-38535 certified Level V (Class S) facility, we are pleased to offer these products to the space marketplace.
Aerospace Information PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Design Tools,Models,Drivers & Software

Title Content Type File Type
Sigma-Delta ADC Tutorial
An interactive illustration showing the behavior of an idealized sigma-delta A/D converter.
Utilities and Conversions HTML
AD7711 Code Examples Code Examples HTML

Evaluation Kits & Symbols & Footprints

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.

SampleSample & Buy

Price, packaging, availability

AD7711 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD7711AAR Status: Production 24 ld SOIC - Wide 24 Ind Tube, 31 $23.10 $19.64 N  Material Info PCN Purchase
AD7711AARZ Status: Production 24 ld SOIC - Wide 24 Ind Tube, 31 $21.67 $18.43 Y  Material Info PCN Purchase
AD7711ANZ Status: Production 24 ld PDIP 24 Ind Tube, 15 $23.83 $18.43 Y  Material Info PCN Purchase
AD7711AQ Status: Production CERDIP GLASS SEAL 24 Ind Tube, 15 $31.93 $24.71 N  Material Info PCN Purchase
AD7711AR Status: Production 24 ld SOIC - Wide 24 Ind Tube, 31 $25.41 $19.64 N  Material Info PCN Purchase
AD7711AR-REEL Status: Last Time Buy 24 ld SOIC - Wide 24 Ind Reel, 1000 - $19.64 N  Material Info PCN/PDN Purchase
AD7711AR-REEL7 Status: Production 24 ld SOIC - Wide 24 Ind Reel, 400 - $19.64 N  Material Info PCN Purchase
AD7711ARZ Status: Production 24 ld SOIC - Wide 24 Ind Tube, 31 $23.83 $18.43 Y  Material Info PCN Purchase
AD7711ARZ-REEL Status: Production 24 ld SOIC - Wide 24 Ind Reel, 1000 - $18.43 Y  Material Info PCN Purchase
AD7711ARZ-REEL7 Status: Production 24 ld SOIC - Wide 24 Ind Reel, 400 - $18.43 Y  Material Info PCN Purchase
AD7711ASQ Status: Production CERDIP GLASS SEAL 24 Mil Tube, 15 $83.42 $70.93 N  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.


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