GENERAL DESCRIPTION

The AD637 is a complete, high accuracy, rms-to-dc converter that computes the true rms value of any complex waveform. It offers performance that is unprecedented in integrated circuit rms-to-dc converters and comparable to discrete and modular techniques in accuracy, bandwidth, and dynamic range. The AD637 computes the true root mean square, mean square, or absolute value of any complex ac (or ac plus dc) input waveform and gives an equivalent dc output voltage. The true rms value of a waveform is more useful than an average rectified signal because it relates directly to the power of the signal. The rms value of a statistical signal relates to the standard deviation of the signal.

FEATURES

High accuracy

0.02% maximum nonlinearity, 0 V to 2 V rms input

0.1% additional error to crest factor of 3

Wide bandwidth

8 MHz at 2 V rms input

600 kHz at 100 mV rms

Computes

True rms

Square

Mean square

Absolute value

dB output (60 dB range)

Chip select/power-down feature allows

Analog three-state operation

Quiescent current reduction from 2.2 mA to 350 µA