RMS-to-DC converter offers high accuracy and dynamic range

August 16, 2011 //By Christoph Hammerschmidt
Analog Devices has developed an integrated true RMS-to-DC converter offering a very high usable dynamic range and the ability to measure extremely low signal levels with high accuracy and no drop in settling time. The AD8436 is targeting remote, portable battery-powered instrumentation, energy and automotive applications where limited board space and outdoor environments are considerations.

The AD8436 precision monolithic true RMS-to-DC converter features AC conversion accuracy to better than ± 0.5 percent. Uniform settling for widely variant input values enables consistent conversion rates with results displayed promptly for near-zero and high-level AC inputs. The AD8436 is immune to temperature, crest factor and supply voltage variations, the vendor claims. Zero DC offset voltages at the converter output simplify calibration. This performance is packed into a compact 4 mm x 4 mm package integrated with a FET input and precision DC buffer amplifiers and consumes only 300 µA of power.

RMS (root mean square) is a fundamental measurement of the magnitude of an AC and DC signal and is a better measure of the power in a signal than simple averaging. RMS-to-DC converters are used in applications where precise, low power measurement of AC/DC signals is the prime objective. The AD8436 system-on-a-chip design computes the precise DC equivalent of the RMS value and provides a level of linearity and accuracy across the entire input range that enables engineers to design systems with 90 dB of dynamic range.

Accpording to Analog Devices, the AD8436 extends the crest-factor to 10 - approximately double the current industry-standard digital solution - with minimal loss of accuracy. It is particularly useful for high transit signals and can be used in designs currently using ADIs low-power, true RMS-to-DC converters such as the AD736 and AD737 with improved performances. The device is laser trimmed and characterised at 300-mV RMS input and comes with dual and single power supplies. The AD8436 is the first RMS-to-DC converter specified to operate in the extended industrial temperature range of -40°C to 125°C. It is also available in a 0°C to 70°C temperature range version.

For data sheet and samples, visit: www.analog.com/AD8436.