Frugal sigma-delta ADC finds handheld niche

Edited by the Electronicstalk editorial team Mar 13, 2003

The latest sigma-delta ADC from Analog Devices combines 24bit resolution with the industry's lowest power consumption and leading-edge accuracy.

The latest sigma-delta ADC from Analog Devices combines 24bit resolution with the industry's lowest power consumption and leading-edge accuracy.

Consuming only 65uA, this new analogue front-end outperforms its closest competitor with 25% lower power dissipation and six times the resolution.

Available in a tiny MSOP-10 package and at a competitive price, it also includes an on-chip buffer and an internal clock generator, making this the most integrated sigma-delta ADC on the market.

Sigma-delta ADCs are ideal for portable instrumentation; sensor, temperature, and pressure measurement; and weigh scale applications.

"As the cost of high-resolution sigma-delta convertors continues to drop, the technology is becoming more accessible, and chip manufacturers are called upon to provide more options for designers of high-resolution measurement systems in which performance, space and power consumption are critical", said Mike Britchfield, Product Line Director for Sigma-Delta Convertors, Analog Devices.

"With this new device, Analog Devices raises the standard for noise performance and continues to push the envelope when it comes to power consumption".

The new 24bit sigma-delta ADC, the AD7791, also comes in a 16bit version, the AD7790.

Both accept differential inputs, which can be buffered or unbuffered; output datarates are software programmable.

Parts without the buffer, and with a fixed 16.6Hz datarate, are also available in 16 and 24bit versions (AD7788/AD7789).

All parts are low-power analogue front-ends for low frequency measurement applications.

Each consumes 65uA when operated with a 3V supply and 75uA when operated with a 5V supply (buffer disabled).

Featuring RMS noise of only 1.5uV, the AD7791 operates from an internally generated clock, eliminating the need for a user-supplied clock source.

Its output data rate is software programmable, allowing rates up to 120Hz.

At the default conversion rate of 16.6Hz, the AD7791 provides simultaneous 50 and 60Hz rejection.

The peak-peak resolution from the part varies with the programmed output data rate.

The device operates from a single 3 or 5V power supply, and supply voltage monitoring is included.

It can be used in single or continuous conversion mode.

The new sigma-delta ADCs come in 10-lead MSOP packaging and are priced as follows in 1000-piece quantities: 24bit AD7791 - $3.83; 16bit AD7790 - $2.95; 24bit AD7789 - $2.95; 16bit AD7788 - $1.99.

Samples and evaluation boards are available now.