In today's complicated world, there are many complicated, difficult to design ADCs from which to choose. The 24-bit AD7780 ADC is not one of them. For ease of use, all of the AD7780 features are controlled by dedicated pins. The on-chip gain, the filter response, and even the power-down and reset functions are controlled from the pins. There are no registers to program, and all the designer needs to do is simply read the conversion results across a 2-wire SPI-compatible interface.

The on-chip PGA has a gain of 1 or 128. In addition, the device has two filter response options. At the 10 Hz and 16.7 Hz update rates, the filter provides a settled conversion in 300 ms and 120 ms, respectively. In addition, simultaneous 50 Hz/60 Hz rejection occurs at both the 10 Hz and 16.7 Hz update rates. Consuming only 380 µA, the AD7780 is particularly suitable for portable or battery-operated products where very low power is a key requirement. The AD7780 also has a power-down mode that allows the user to switch off the power to the bridge sensor and power down the AD7780 when not converting, thus increasing the battery life of the product.

The AD7781 is a 20-bit version of the AD7780 and is available in two noise grades. The AD7780/AD7781 operate with a power supply from 2.7 V to 5.25 V and are available in a narrow-body, 14-lead SOIC package and 16-lead TSSOP package.

For more information on ADI's Σ-Δ converters, visit
www.analog.com/sigmadelta.

Online ADC Simulation, Software, and Behavioral Models Help Simplify the Design Process

ADI's ADIsimADC online evaluation and simulation platform accurately models the typical performance characteristics of many of our high speed converters. ADI provides a library of popular product models, and there are three tools that use these models to give designers consistent simulation results at different stages of the design and evaluation process. These tools are ADIsimADC, VisualAnalog, and ADC Analyzer™

ADIsimADC is ADI's analog-to-digital behavioral model that faithfully reproduces the errors associated with both static and dynamic features such as ac linearity, clock jitter, and many other product specific anomalies. For simple product selection, this Web-based application is accessible via the product pages of the devices that are supported by ADIsimADC. The tool requires no downloads and allows control of the test conditions and design specific performance plots. Results are graphed to reduce the uncertainty about how a part will perform in a given application. The tool also allows input of desired operating conditions and required performance levels and will recommend suitable devices to the user.

ADC Analyzer is a downloaded tool that runs the behavioral models, measures ADC performance with varying input frequencies and sample rates, and configures evaluation boards.

VisualAnalog takes this concept further by allowing designers to customize their input signal and data analysis. An input signal can be constructed from sine waves, noise sources, and vector data to see how an ADC will perform in real-world conditions. The VisualAnalog software package combines a powerful set of simulation and data analysis tools with a user-friendly graphical interface.

Now, ADI has created three brief technical videos that describe the operation, features, and benefits of these online simulation tools. The videos and tools are now available at www.analog.com/ADIsimADC.

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