Overview
The AD637AQ, produced by Analog Devices Inc., is a high-precision, wideband RMS-to-DC converter. This integrated circuit is designed to compute the true root mean square (rms), mean square, or absolute value of any complex AC (or AC plus DC) input waveform, providing an equivalent DC output voltage. The AD637AQ offers unprecedented accuracy, bandwidth, and dynamic range, comparable to discrete and modular techniques. It is particularly useful because the true rms value of a waveform relates directly to the power of the signal and the standard deviation of statistical signals.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Maximum Nonlinearity (0 V to 2 V rms input) | 0.02% | % | ||
| Additional Error to Crest Factor of 3 | 0.10% | % | ||
| Bandwidth at 2 V rms input | 8 MHz | Hz | ||
| Bandwidth at 100 mV rms input | 600 kHz | Hz | ||
| Quiescent Current | 350 μA | 2.2 mA | mA | |
| Operating Temperature Range | -55°C | +125°C | °C | |
| Package Types | 14-lead SBDIP, 14-lead CERDIP, 16-lead SOIC_W |
Key Features
- High accuracy with 0.02% maximum nonlinearity for inputs from 0 V to 2 V rms.
- Wide bandwidth, supporting signals up to 8 MHz at 2 V rms input and 600 kHz at 100 mV rms input.
- Computes true rms, mean square, or absolute value of complex waveforms.
- Direct dB output with a 60 dB range available on a separate pin.
- Externally programmed reference current to select the 0 dB reference voltage between 0.1 V and 2.0 V rms.
- Chip select/power-down feature to reduce quiescent current from 2.2 mA to 350 μA, facilitating use in remote or handheld applications.
- Input circuitry protected from overload voltages, and outputs go to high impedance state when powered down.
- Laser wafer trimmed for rated performance without external trimming.
- On-chip buffer amplifier can be used as an input buffer or in an active filter configuration.
Applications
- Precision measurement in industrial control systems where accurate rms values are crucial.
- Remote or handheld applications where low power consumption is critical.
- Wideband true rms multiplexing by tying multiple AD637s together.
- Signal processing and conditioning in various electronic systems.
- Measurement of signals with high crest factors up to 10 with less than 1% additional error.
Q & A
- What is the primary function of the AD637AQ?
The AD637AQ computes the true root mean square (rms), mean square, or absolute value of any complex AC (or AC plus DC) input waveform and provides an equivalent DC output voltage.
- What is the maximum nonlinearity of the AD637AQ for inputs from 0 V to 2 V rms?
The maximum nonlinearity is 0.02%.
- What is the bandwidth of the AD637AQ at 2 V rms input and 100 mV rms input?
The bandwidth is 8 MHz at 2 V rms input and 600 kHz at 100 mV rms input.
- How does the chip select/power-down feature work?
The chip select/power-down feature reduces the quiescent current from 2.2 mA to 350 μA when the rms function is not in use, and the output goes to a high impedance state when powered down.
- What types of packages are available for the AD637AQ?
The AD637AQ is available in 14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages.
- How is the 0 dB reference voltage selected?
The 0 dB reference voltage can be selected using an externally programmed reference current to correspond to any level between 0.1 V and 2.0 V rms.
- What is the operating temperature range of the AD637AQ?
The operating temperature range is from -55°C to +125°C.
- How is the input circuitry protected?
The input circuitry is protected from overload voltages in excess of the supply levels, and the inputs are not damaged by input signals if the supply voltages are lost.
- What is the purpose of the on-chip buffer amplifier?
The on-chip buffer amplifier can be used either as an input buffer or in an active filter configuration to reduce ac ripple and increase accuracy.
- Why is the true rms value more useful than an average rectified signal?
The true rms value relates directly to the power of the signal and the standard deviation of statistical signals, making it more useful than an average rectified signal.
