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AD7781:  20-Bit, Pin-Programmable, Ultralow Power Sigma-Delta ADC

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 ...More

AD7781:  20-Bit, Pin-Programmable, Ultralow Power Sigma-Delta ADC

Product Description

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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TOOLS, SOFTWARE & SIMULATION MODELS

  • 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
  • Resolution (Bits): 20bit
  • T-Put Rate: 16.7SPS
  • # Chan: 1
  • Supply V: Single(+3),Single(+3.3),Single(+3.6),Single(+5)
  • Pwr Diss: 2.1mW
  • Interface: Ser,SPI
  • Ain Range: ± (Vref/Gain) ,10V p-p,78 mV p-p
  • SNR (dB): n/a
  • Pkg Type: SOIC,SOP

Functional Block Diagram for AD7781

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Similar Products

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Part# Bits Throughput Rate # of Inputs Operating Pwr Diss
AD7781 20 16.7SPS 1 2.1mW
AD7790 16 120SPS 1 800µW
AD7796 16 123SPS 1 1.6mW
AD7466 12 200KSPS 1 900µW
AD7791 24 120SPS 1 800µW
AD7151 12 100SPS 1 300µW
AD7797 24 123SPS 1 1.6mW
AD7153 12 200SPS 1 432µW
AD7467 10 200KSPS 1 630µW
AD7468 8 200KSPS 1 570µW
AD7703 20 4KSPS 1 37mW
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The package for this IC (i.e. DIP, SOIC, BGA). An Evaluation Board is a board engineered to show the performance of the model, the part is included on the board.

For detailed drawings and chemical composition please consult our  Package Site

Pin Count
Pin Count is the number of pins, balls, or pads on the device. Pin-out diagrams & pin function descriptions may be found in the datasheet.

Temperature Range
This is the acceptable operating range of the device. The various ranges specified are as follows:
  • Commercial: 0 to +70 degrees Celsius
  • Military : -55 to +125 degrees Celsius
  • Industrial: Temperature ranges may vary by model. Please consult the datasheet for more information.
  • Automotive: -40 to +125 degrees Celsius
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Due to environmental concerns, ADI offers many of our products in lead-free versions. For more information about lead-free parts, please consult our Pb (Lead) free information page.

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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.
**Sample availability may be better than production availability. Please enter samples into your cart to check sample availability.