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Overview

Features and Benefits

  • Pin-programmable filter response
    Update rate: 10 Hz or 16.7 Hz
  • Pin-programmable in-amp gain
  • Pin-programmable power-down and reset
  • Status function
  • Internal clock oscillator
  • Internal bridge power-down switch
  • Current:
    115 μA typical (Gain = 1)
    330 μA typical (Gain = 128)
  • Simultaneous 50 Hz/60 Hz rejection
  • Please see data sheet for additional features

Product Details

The AD7781 is a complete low power front-end solution for bridge sensor products, including weigh scales, strain gages, and pressure sensors. It contains a precision low power 20-bit sigma-delta (Σ-Δ) ADC, an on-chip, low noise programmable gain amplifier (PGA), and an on-chip oscillator.

Consuming only 330 μA, the AD7781 is particularly suitable for portable or battery-operated products where very low power is required. The AD7781 also has a power-down mode that allows the user to switch off the power to the bridge sensor and power down the AD7781 when not converting, thus increasing the battery life of the product.

For ease of use, all the features of the AD7781 are controlled by dedicated pins. Each time that a data read occurs, eight status bits are appended to the 20-bit conversion. These status bits contain a pattern sequence that can be used to confirm the validity of the serial transfer.

The on-chip PGA has a gain of 1 or 128, supporting a full-scale differential input of ±5 V or ±39 mV. The device has two filter response options. The filter response at the 16.7 Hz update rate provides superior dynamic performance. The settling time is 120 ms at this update rate. At the 10 Hz update rate, the filter response provides better than -45 dB of stop-band attenuation. In load cell applications, this stop-band rejection is useful to reject low frequency mechanical vibrations of the load cell. The settling time is 300 ms at this update rate. Simultaneous 50 Hz/60 Hz rejection occurs at both the 10 Hz and 16.7 Hz update rates.

The AD7781 operates with a power supply from 2.7 V to 5.25 V. It is available in a narrow body, 14-lead SOIC package and in a 16-lead TSSOP package.

Applications

  • Weigh scales
  • Pressure measurement
  • Industrial process control
  • Portable instrumentation

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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.

Evaluation Kits (1)

Documentation & Resources

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  • Data Sheets (1)
  • Application Notes (1)
  • User Guides (1)
  • Circuit Note (1)
  • Technical Articles (2)
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    Software & Systems Requirements

    Device Drivers

    WIKI

    AD7780 IIO Low Power Sigma-Delta ADC Linux Driver

    Evaluation Software

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    341517 kB

    AD7781 Evaluation Board Software
    ZIP
    1419 kB

    AD7781 Evaluation Software Labview Source Code

    Tools & Simulations

    Design Tools

    Sigma-Delta ADC Tutorial

    An interactive illustration showing the behavior of an idealized sigma-delta A/D converter.

    Reference Designs (1)

    Design Resources

    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.

    AD7781 Material Declaration
    Quality And Reliability
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    PCN-PDN Information

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    • AD7781CRZ Production

    Support & Discussions

    AD7781 Discussions

    RE: AD7781 PCB routing Guideline for Analog inputs
    Digital Interface FAQ - Sigma Delta ADC
    RE: Sigma-Delta ADC low frequency attenuation
    All AD7781 Discussions
    AD7781 Contact ADI Technical Support »
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