Overview
The AD637ARZ, produced by Analog Devices Inc., is a high-accuracy, wideband RMS-to-DC converter. This integrated circuit 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. The AD637ARZ offers unprecedented performance in 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 | Comments |
|---|---|---|---|---|---|
| Nonlinearity (0 V to 2 V rms input) | 0.02% | ||||
| Additional Error to Crest Factor of 3 | 0.1% | ||||
| Bandwidth at 2 V rms input | 8 MHz | ||||
| Bandwidth at 200 mV rms input | 600 kHz | ||||
| dB Output Range | 60 dB | ||||
| Quiescent Current | 350 | 2.2 | mA | Powered down to 350 µA | |
| Input Offset Voltage | ±0.8 | ±2 | mV | ||
| Input Current | ±2 | ±10 | nA | ||
| Input Resistance | 108 | Ω | |||
| Output Current | -0.13 | +5 | mA | ||
| Short-Circuit Current | 20 | mA | |||
| Small Signal Bandwidth | 1 | MHz | |||
| Slew Rate | Not specified in the provided sources |
Key Features
- High Accuracy: 0.02% maximum nonlinearity for inputs from 0 V to 2 V rms, with an additional 0.1% error for crest factors up to 3.
- Wide Bandwidth: Measures signals up to 600 kHz at 200 mV rms and up to 8 MHz at inputs above 1 V rms.
- Crest Factor Compensation: Allows measurements of signals with crest factors of up to 10 with less than 1% additional error.
- dB Output: Direct dB value of the rms output with a range of 60 dB available on a separate pin.
- Chip Select/Power-Down Feature: Reduces supply current from 2.2 mA to 350 µA during periods when the rms function is not in use, facilitating low power consumption in remote or handheld applications.
- Input Protection: Input circuitry protected from overload voltages in excess of the supply levels, ensuring no damage from input signals if supply voltages are lost.
- Laser Wafer Trimming: Achieves rated performance without external trimming, requiring only a capacitor to set the averaging period.
- On-Chip Buffer Amplifier: Can be used as an input buffer or in an active filter configuration to reduce ac ripple and increase accuracy.
Applications
- Remote and Handheld Devices: The low power consumption feature makes it ideal for remote or handheld applications where precision rms measurement is critical.
- Signal Processing and Measurement: Useful in various signal processing and measurement applications where accurate rms values are necessary, such as in audio, medical, and industrial equipment.
- Multiplexing: Can be used to form a wideband true rms multiplexer by tying several AD637s together, especially when powered down to a high impedance state.
Q & A
- What is the primary function of the AD637ARZ?
The AD637ARZ is a high-accuracy, wideband RMS-to-DC converter that computes the true RMS value of any complex waveform and provides an equivalent DC output voltage.
- What is the maximum nonlinearity of the AD637ARZ for inputs from 0 V to 2 V rms?
The maximum nonlinearity is 0.02% for inputs from 0 V to 2 V rms.
- What is the bandwidth of the AD637ARZ at 2 V rms input?
The bandwidth is up to 8 MHz at 2 V rms input.
- How does the chip select/power-down feature work?
The chip select connection allows the user to decrease the supply current from 2.2 mA to 350 µA during periods when the rms function is not in use, and the output goes to a high impedance state when powered down.
- 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.
- What types of packages are available for the AD637ARZ?
The AD637ARZ is available in 16-lead SOIC_W packages among others.
- How does the AD637ARZ handle crest factor compensation?
The AD637ARZ allows measurements of signals with crest factors of up to 10 with less than 1% additional error.
- What is the range of the dB output available on the AD637ARZ?
The dB output range is 60 dB, available on a separate pin.
- Is external trimming required for the AD637ARZ?
No, the AD637ARZ achieves rated performance without external trimming due to laser wafer trimming, requiring only a capacitor to set the averaging period.
- What are the temperature ranges for different accuracy grades of the AD637ARZ?
The AD637ARZ is available in various accuracy grades for different temperature ranges: commercial (0°C to 70°C), industrial (−40°C to +85°C), and military (−55°C to +125°C).
