Features and Benefits
- Charge-Balancing ADC
24 Bits, No Missing Codes
- 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)
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.
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Documentation & Resources
AN-931: Understanding PulSAR ADC Support Circuitry (Rev. 0)2/14/2015
AN-202: An IC Amplifier User’s Guide to Decoupling, Grounding, and Making Things Go Right for a Change (Rev. B)2/14/2015
AN-389: Using Sigma-Delta Converters-Part 22/14/2015
AN-388: Using Sigma-Delta Converters-Part 12/14/2015
AN-311: How to Reliably Protect CMOS Circuits Against Power Supply Overvoltaging3/8/2008
AN-607: Selecting a Low Bandwidth (<15 kSPS) Sigma-Delta ADC (Rev. E)10/12/2006
AN-615: Peak-to-Peak Resolution Versus Effective Resolution (Rev. 0)12/21/2004
AN-397: Electrically Induced Damage to Standard Linear Integrated Circuits:11/18/2002
AN-283: Sigma-Delta ADCs and DACs9/24/2002
AN-553: Adjusting the Calibration Coefficients on the AD771X Family of ADCs1/1/2000
AN-406: Using the AD771X Family of 24-Bit Sigma-Delta A/D Converters1/1/2000
AN-366: Evaluation Board for the AD7711 24-Bit Sigma-Delta ADC1/1/2000
Designing Power Supplies for High Speed ADC2/1/2012
Delta-Sigma Rocks RF, As ADC Designers Jump On Jitter1/12/2006
Part 2: Circuit Suggestions Using Features and Functionality of New Sigma-Delta ADCs6/1/2002
Part 1: Circuit Suggestions Using Features and Functionality of New Sigma-Delta ADCs10/1/2001
Transducer/Sensor Excitation and Measurement Techniques8/1/2000 Analog Dialogue
Software & Systems Requirements
AD7711 Code Examples
Tools & Simulations
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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