Overview
The AD637KQ, produced by Analog Devices Inc., is a high-accuracy, 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 and provide an equivalent DC output voltage. The AD637KQ 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 the signal.
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 | 600 kHz | Hz | ||
| Supply Voltage Range | ±3V | ±18V | V | |
| Quiescent Current (Active) | 2.2 mA | mA | ||
| Quiescent Current (Power-Down) | 350 µA | µA | ||
| Input Resistance | 6.4 kΩ | 8 kΩ | 9.6 kΩ | kΩ |
| Input Offset Voltage | ±0.2 mV | ±0.5 mV | mV | |
| Output Offset Voltage | ±0.5 mV | ±1 mV | mV | |
| Temperature Range (Grade K) | 0°C | 70°C | °C |
Key Features
- High Accuracy: 0.02% maximum nonlinearity for inputs from 0 V to 2 V rms, and 0.10% additional error for crest factors up to 3.
- Wide Bandwidth: Measures signals up to 8 MHz at 2 V rms input and up to 600 kHz at 100 mV rms input.
- Crest Factor Compensation: Allows measurements of signals with crest factors up to 10 with less than 1% additional error.
- dB Output: Direct dB value of the rms output with a 60 dB range available on a separate pin.
- Chip Select/Power-Down Feature: Reduces quiescent current from 2.2 mA to 350 µA and allows multiple AD637s to be tied together for a wideband true rms multiplexer.
- Input Protection: Input circuitry protected from overload voltages in excess of supply levels.
- Laser Wafer Trimming: Achieves rated performance without external trimming.
- On-Chip Buffer Amplifier: Can be used as an input buffer or in an active filter configuration to reduce ac ripple.
Applications
- Remote and Handheld Applications: The low power consumption feature makes it ideal for remote or handheld devices where precision rms measurement is required.
- Industrial and Commercial Environments: Suitable for applications requiring high accuracy and wide bandwidth in various temperature ranges.
- Signal Processing and Measurement: Useful in applications that require the true rms value of complex waveforms, such as in audio, medical, and industrial instrumentation.
- Multiplexing: Can be used to form a wideband true rms multiplexer by tying multiple AD637s together.
Q & A
- What is the primary function of the AD637KQ?
The AD637KQ 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 AD637KQ 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 AD637KQ at 2 V rms input?
The bandwidth is up to 8 MHz at 2 V rms input.
- How does the crest factor compensation work in the AD637KQ?
The AD637KQ allows measurements of signals with crest factors up to 10 with less than 1% additional error.
- What is the purpose of the chip select/power-down feature?
This feature reduces the quiescent current from 2.2 mA to 350 µA and allows multiple AD637s to be tied together for a wideband true rms multiplexer.
- How is the input circuitry of the AD637KQ protected?
The input circuitry is protected from overload voltages in excess of the supply levels.
- What types of packages are available for the AD637KQ?
The AD637KQ is available in hermetically sealed 14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages.
- What is the temperature range for the AD637KQ (Grade K)?
The temperature range is from 0°C to 70°C.
- How does the on-chip buffer amplifier function?
The on-chip buffer amplifier can be used either as an input buffer or in an active filter configuration to reduce ac ripple.
- What is the significance of the dB output feature?
The dB output feature provides a direct dB value of the rms output with a 60 dB range, available on a separate pin.
