Analog Devices Inc. AD637JQ

The AD637JQ from Analog Devices Inc. is a high-accuracy, monolithic RMS-to-DC converter designed to compute the true RMS value of any complex waveform. This component offers unprecedented performance in integrated circuit RMS-to-DC converters, comparable to discrete and modular techniques in terms of accuracy, bandwidth, and dynamic range. It can measure the true root mean square, mean square, or absolute value of any complex AC (or AC plus DC) input waveform and provide an equivalent DC output voltage.

• 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.
• Direct dB Output: Provides a direct dB value of the rms output with a range of 60 dB on a separate pin.
• Externally Programmable Reference Current: Allows the user to select the 0 dB reference voltage between 0.1 V and 2.0 V rms.
• Chip Select/Power-Down Feature: Reduces supply current from 2.2 mA to 350 µA during periods of inactivity, and the output goes to a high impedance state when powered down.
• Input Protection: Input circuitry is protected from overload voltages in excess of the supply levels.
• Laser Wafer Trimming: Achieves rated performance without external trimming, with the only external component required being a capacitor for setting 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.

• Remote and Handheld Applications: The low power consumption feature makes it ideal for remote or handheld devices where minimum power is critical.
• True RMS Multiplexing: Multiple AD637s can be tied together to form a wideband true rms multiplexer due to the high impedance state when powered down.
• Industrial and Commercial Environments: Available in various accuracy grades for different temperature ranges, making it suitable for both commercial and industrial applications.

1. What is the maximum nonlinearity of the AD637JQ?

   The AD637JQ has a maximum nonlinearity of 0.02% for inputs from 0 V to 2 V rms.

2. What is the bandwidth of the AD637JQ at different input levels?

   The AD637JQ can measure signals up to 600 kHz at 200 mV rms and up to 8 MHz at inputs above 1 V rms.

3. Does the AD637JQ provide a direct dB output?

   Yes, the AD637JQ provides a direct dB value of the rms output with a range of 60 dB on a separate pin.

4. How does the chip select/power-down feature work?

   The chip select feature reduces the supply current from 2.2 mA to 350 µA during periods of inactivity, and the output goes to a high impedance state when powered down.

5. What external components are required for the AD637JQ?

   The only external component required is a capacitor that sets the averaging period, which also determines low frequency accuracy, ripple level, and settling time.

6. Is the input circuitry of the AD637JQ protected from overload voltages?

   Yes, the input circuitry is protected from overload voltages in excess of the supply levels.

7. What are the different accuracy grades available for the AD637JQ?

   The AD637JQ is available in accuracy Grade J and Grade K for commercial temperature range, Grade A and Grade B for industrial range, and Grade S for military temperature range.

8. Can multiple AD637JQs be used together to form a multiplexer?

   Yes, multiple AD637JQs can be tied together to form a wideband true rms multiplexer due to the high impedance state when powered down.

9. 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.

10. What are the typical package options for the AD637JQ?

    The AD637JQ is available in hermetically sealed, 14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages.