AD637AQ

The AD637AQ from Analog Devices is a complete, high-accuracy, wideband RMS-to-DC converter designed to compute the true RMS value of any complex waveform. It offers performance comparable to discrete and modular techniques, providing unprecedented accuracy, bandwidth, and dynamic range in an integrated circuit.

Key features include a maximum nonlinearity of 0.02% for inputs from 0 V to 2 V rms, and an additional error of less than 0.1% for crest factors up to 3. The device boasts a wide bandwidth, operating at 8 MHz for inputs above 1 V rms and 600 kHz for inputs as low as 100 mV rms. It can compute the true root mean square, mean square, or absolute value of AC or AC plus DC input waveforms, outputting an equivalent DC voltage. A separate pin provides a direct dB output with a 60 dB range.

The AD637AQ is suitable for applications requiring precise RMS measurements. Its chip select/power-down feature allows quiescent current reduction from 2.2 mA to 350 µA, making it ideal for low-power and handheld applications. When powered down, the output enters a high-impedance state, enabling multiple AD637AQ devices to form a wideband true RMS multiplexer.

This converter is available in a 14-CERDIP package and is through-hole mounted. The input circuitry is protected against overload voltages, and the device is laser wafer trimmed for rated performance without external adjustments. The only required external component is a capacitor for setting the averaging period, which also influences low-frequency accuracy, ripple level, and settling time.