Date: 19/08/2011

True RMS-to-DC converter with 100 µV to 3 V dynamic ranges

Analog Devices, Inc. has unveiled AD8436, a precision, low power, monolithic true RMS-to-DC converter that offers a usable dynamic range and to measure extremely low signal levels with high accuracy and no drop in settling time.

Key features of AD8436 include:
Instantly computes true RMS value
Fast and constant settling time at all input levels
Wide usable dynamic range: 100 uV RMS to 3 VRMS (8.5 V p-p) full-scale
Input frequency range: 65 kHz for additional 1 percent error
Low power: 300 µA typical at ±2.4 V
Accuracy: ±10 µV ± 0.5 percent of reading max
System-on-a-chip includes FET input buffer with precision gain setting resistors, output buffer
Supply range: Dual: +/-2.4 V to +/-18 V, Single: 4.8 V to 36 V

The AD8436 is immune to temperature, crest factor and supply voltage variations and Zero DC offset voltages at the converter output simplify calibration. The AD8436 is suitable for remote, portable battery-powered instrumentation, energy and automotive applications where limited board space and outdoor environments are considerations.

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, as per Analog Devices.

According to Analog Devices, the AD8436 extends the crest-factor to 10 - approximately double the current industry-standard digital solution - with minimal loss of accuracy. The AD8436 is the first RMS-to-DC converter specified to operate in the extended industrial temperature range of -40°C to 125°C, claims Analog Devices. It is also available in a 0°C to 70°C temperature range version.

Available: Now in production volumes
Package: 4.95 20-lead LFCSP4 mm x 4 mm
Price: AD8436A - $4.9520 each for 1K units
AD8436JZ- $2.9520 each for 1K units